What Could A Painless, Non-moving Bump On My Shin That Appears Only When I Bend Down Be?

Hello! I have this small bump on my shin that only comes out when I bend down. It s about the size of the top of my thumb, it doesn t move and it doesn t hurt. I ve had it for a few months (I m unsure exactly when I first noticed it) and its been there a while and has never grown. I ve been feeling completely fine health wise as well.