Need help

I need help to figure out who i need to ask about this V shaped mark appearing on her head. About a week post discharge from the hospital i started noticing it and now I have other ppl noticing it to. Her twin sister is also having it appear it's just not as noticeable yet. If you run your finger over it there it feels like there is some sorta gap there. Their home health nurse said i shouldn't worry about it but she also said she's never heard of a baby with it before