My 17 year old son finally gave in to the heat yesterday and wore shorts, I noticed that he has what appears to be quite a deep hole on his leg. He said it's been there a couple of weeks and he hasn't said anything because it's not bothering him. He doesn't recollect hurting himself, any ideas what it could be, insect bite maybe, could it be an ulcer (but surely he's too young). He's adamant he won't go to the doctor.