My dd2 was born with this, it refills every time it is squeezed. Doctor wasn't fussed about it, it is showing no signs of going and I'm wondering if it is a cyst of some kind? I didn't realise babies could be born with something like this though as it's not closed under the skin like I would expect!
It looks and acts like my old piercing holes with the emptying and refilling but unless she's really rebellious without me realising, I don't think she got piercings in utero 