Hi - I Bumped My Leg On A Dull Piece

Hi - I bumped my leg on a dull piece of metal sticking out. It did not break the skin at all. I thought, hmmmm... that is gonna cause a bruise but it did not seem to bad really. I did take some ibuprophen and the pain diminished. When I got home i took off my pants to look at it and it has a small bruise like I thought but it also has a lump the size of 1/2 a softball, it is very hard and discolored. Also very tender to the touch. Is this just additional bruising from the way i hit it? Or should I be worried about it at all?