Indentation on forehead doesn’t seem to be healing

I noticed this indentation on my head a few months ago and doesn’t appeal to be getting any better. Its an indent and black around there crater. Almost looks like something in it. Gives me no bother apart from was a bit itchy on sat.

Came out of nowhere and actually just after a haircut I thought it was a stubbly bit of hair. When 1st noticed I did try to burst but couldn’t anyone seen anything like this?