Depending on the position you were in while he was playing with you, it could've been your hymen or your pubic bone, in certain positions the pubic bone will close off your vaginal opening a bit more. I definitely notice this when changing positions without pulling out during sex, leaning certain ways will feel super uncomfortable because of the pubic bone. Has he ever been with a female before, as in, does he know what a healthy vagina looks like?
Have you ever penetrated yourself with your fingers? If so, did it feel tight? You might have a microperforated hymen, or sometimes females are born with vaginas that are too tight for normal penetration, or if it feels like a lump, it could be a cyst. I'm assuming you haven't had a pelvic exam before? It might be a good idea to go get checked out if something seems abnormal.