Bruising is internal bleeding. You want to get it checked out *now*, and for goodness sake keep it up and rested. *Don't * overdo it or you'll risk all sorts of complications

I did something similar a few years back and now have a permanently torn thigh muscle. After 6 weeks I had to have a pint of excess and misplaced fluid drained from the injured area.

I don't do physics, though, sorry

Paws