Why My Knee Is Stiff Post Fall?

I fell really hard on both my knees (on carpet), and my left knee took the worst part of the hit. I went to the ER and they said nothing was 'broken'. I had swelling in the front and a lump on the outside of my knee they said could be a tendon or a blood clot. It seems to be getting better, the lump is now a big bruise and the lump is smaller. No pain to stand or walk, but stiff when I try to bend it all the way. Should I have a specialist look at it?