2 days ago I hit the top of my head on car door suffer with health anxiety so was really scared now all day have a slight ache/pain in the spot I hit?

Actually that sounds. pretty normal if you have a contusion from a blunt injury to your head. If that is your only symptoms then I would try not fret. Take care.
Watch it! Sorry for the feeble pun. But to be reassuring, the slight pain is likely to be only a bruise. Still it can take days to go away. If you did not lose consciousness or have blurry vision the internal damage (while not nothing) probably was minimal. If it happened often, like it does in some sports, it could add up to a problem, but a few in a life are usually okay. If you feel worse, have an exam.