My PVA chick has finally hatched but has a cysty like lump on his head

Hi I was wondering if anyone can help. I got some eggs through the post to incubate, on the first day I accidently dropped one so that the side of the shell was dented to the size of a penny, I read on the net about fixing it with pva glue so i did, it developed normally. It has finally hatched this morning 36 hours after the rest but my little chick has a lump on the back of his head which is not covered by feathers, it looks like a cyst I have touched it and it is very soft and fluid filled, he seems fine apart from that. Does anyone know if he could have injured himself during the hatching process or have i caused this by dropping the egg? and also has this happened to anyone before and does the lump resolve itself? Please help :O)
Ke111y