My knee is swollen and it wont go dwn :/?

i got hit by a ford f-150 at school walking on a pedestrian walk on may 24th. cars had stopped to let me and my friend go across it. so this girl went around the stopped cars and hit me with the front of the car and my friend got hit with the mirror in the face and got knocked out. okay thts what happend, my knee is swollen because of it. it hurts and i cant bend it at all. and tomorrow im going to have an mri done and like im scared i play basketball and im scared i wont be able to play again can somebody please help me?!