I have a hematoma on leg that is the size of a football. I have had this for two weeks now since the injury. It is burning inside when I stand up.?

Reabsorbs slowly. This collection of blood will soften up and reabsorbs slowly. It may take several months, though. Heating pads will make it feel better in the meantime.
Get Evualuated. That is awful large and should be evaluated. It might be able to be drained or worse case removal in operating room if continues to be a problem. The burning could be due to nerve injury. Either way get it evaluated so that you can know what it is and receive proper treatment.