When I got him at the pet store he had a scab on his head. Soon after I got him home it fell off and he had what looked like a perfect round hole and you could actually see his skull. I was already attached to him so taking him back was out of the question. I have been putting antibiotic ointment on it 2-3 times a week and it is finally starting to fill in. Can no longer see the skull. It has never looked irritated or infected. He has a little trouble getting the shed off at that spot and I usually have to hold a damp rag over it for a couple min. then I can sort of rub it off. I think it may leave a scar but it will just make him even more handsome I guess!
I have no idea what may have caused it.... he was just a baby when we got him (54 gm).