In The Locker Room At My School There Are Small

In the locker room at my school there are small lockers at about the height of our feet, and they have these small hook like things poking out of them were you put the lock. Well as I was getting dressed I accidentally slammed my foot down on it and got a small little purple bruise. The pain and swelling went away in a couple days, but it has been a little over a month since then and it is still there. In that time it had also turned a dark black. I am worried, can you tell me what's wrong?