My husband(40) has got a dent in the back of his head . This was not there last week, I shave his head, it has just appeared he doesnt recall doing anything or banging it. It is quite a prominant dip in the back of his head/skull, even my 5 year old noticed it. He is now complaining it is sore , but we have all been prodding it, so nothing to worry about on that side. I just wondered if this was anything to be worried about?