What Causes Swelling In Legs?

I got hit by a car about two weeks ago, i went to the hospital and they discharged me, with only a bruised leg, a minor injury because i could walk easily, however it is now two weeks after the incident and my leg is still swollen, well i say swollen however all swelling seems to have subsided, although, my leg appears to have a liquid inside, when i rest for a while the liquid seems to lessen but not go completely, returning when i walk or do anything, i am just worried about what this liquid could be, the doctors say that my leg has just been bruised, but could it be broken, also i wouldn't say it hurts that much anymore, any help, advice appreciated, thanks.