Have you heard this story - hurt by projection?

I attended a training course run by a renowned healer in my area at the weekend. I won't mention his name.

Anyway, this guy can do all kinds of weird things, so I asked him if he astral projects and his answer was that he used to dabble but didn't any more as it can be very dangerous. Story goes he had a stall at a psychic fair type of thing and some guy came up saying 'can you cure this?', and showed him the back of his neck where the muscle connecting under the back of his skull had completely disconnected. The guy has apparently written a book on astral projection and had in the words of the guy I was talking to 'tried to do something clever' either in or connected with the Egyptian pyramids while projecting, and received the injury as a result. I couldn't get any more of the story or the name of the guy who wrote the book because this healer was concerned he might put ideas into my head to try something stupid.

Anyone heard of this story or have an idea who the author could be?

Never heard of him. The only caveats with projection I have heard are as follows:
1) That you can be possessed when out. This is faulty because when you project you don't leave your body empty, you move your conscious awareness into your expanded energy body. There is no 'empty body' left behind.
2) Meditation- The meditative states associated with projection can bring about emotional/mental problems. This is partly true, but you will not be 'driven crazy' if you don't have a tendency towards certain types of problems. Because the liminal states you get into can let you 'see' stuff you don't usually see when awake, it can be misunderstood and unnerving, to say the least.
3) There have been reports of people being attacked in places that have psychic protection. I can attest to this being true (at least for me)- but the attack was not harmful- you can compare it to having a nightmare while completely aware.
I can't speak for what someone else says happened, but most of the prohibitions against it I have seen in the net are usually religious-based.

I would start out with saying it is extremely unlikely.

Given the rough outline you give here, I would give the following caveat: It is possible to hurt yourself with meditation or energy work if you ignore all safety precautions, develop an obsession in doing them, ignore all signals your body and mind will generate to warn you and persist, and are generally tenacious enough to push on in these circumstances.

Generally not knowing your limits and pushing on is a way to get hurt in any discipline, be it sports or be it nonphysical exploration. Just as a muscle needs to be developed carefully before being put to hard use, the mind needs to be prepared and honed before certain experiences can be had. That's one reason why drugs for nonphysical exploration are considered harmful - they disable the natural security mechanisms of the human mind against experiencing what it is not prepared for. Similarly, the kind of mindset described above does a similar thing - it breaks down the natural security mechanisms.

Extreme energetic practices exist that are said to be able to have very uncomfortable side effects. As energy effectively has to ground itself out through the body, such practices can also cause harm and pain in the body. A "clever thing with the pyramids" seems for me to be a reference to magical work in traditions like the hermetic and other ones. Again, advanced practices here are not recommended without the necessary groundwork.

How much groundwork is needed is hard to assess. There are claims to traumatic Kundalini experiences and effortless rising of the serpent current out there. It's hard to ascertain as to what's true, but I think it's better to err on the side of caution.

If one tries to mind one's own limits, including the signals mind and body generate (these include signs of mental, emotional or physical stress), one is unlikely to come to any harm, or likely to find ways to evade harm. Harm as described in the original post is very unlikely, and in my expectation would not come about randomly.

This jogged a memory of a guy I work with at times who is quite high up in the Akido martial arts and meditate allot.
He told me when his master passed away who was a pupil of the Akido inventor he would in his dreams have moments where
they would talk and spare together like they used to and then end up waking up with bruises..


Zethor

I have heard of one story like this where a fellow I was chatting with over the internet told me he had a dream where he encountered a demon or some sort of monster. It slashed him with its claws and when he woke up he had claw marks. I think this might have to do with what my guide told me that physical and nonpsysical reality are actually the same thing. Though I think in most instances attacks you have in the astral or other plains won't effect your physical body so unless you plan on mixing it up with some really powerful entities that may have access to physical reality I wouldn't worry about it.