What Causes Swelling And Bone Popping Out Of Knee After Fall?

i run track at my school. in my last meet i did long jump my steps were messed up and went off the wrong foot. It started to hurt the next day when walking up and down stairs and at practice. My knee is a little bit swollen and when bent at a 90-80dregee angle a bone has popped out on the right side of my right knee.also on the right side it feels kind of sponge like. Do you know whats wrong or what i can do to help it?