This kitten I found has something on its head that I'm not sure about....?

I found this kitten today. It seems to be around 7 weeks old, and besides the fact that it's skinny from not eating for awhile, it seems to be pretty healthy.
Although I noticed while I was petting it that on the top of its head/skull it has this weird feeling. When I rub it it makes this like 'crackle' sound and it feels like plastic. It seems to be either skin loose or something else...I've never seen this so I don't know if it's a sign of head trauma or what. But if anyone has any ideas on what this would be I would appreciate some answers.
Also I don't know if this is any serious injury, so should I contact my vet?

Thank you.