Suggest Treatment For Knee And Leg Pain After An Injury

I hurt my right leg yesterday. On the back of the calf, on the right side, right under the back of the knee, is giving me sharp pain. I stretched the muscle yesterday and it felt better, but for some reason, this area is giving my alot of pain. When i walk, sometimes I have to limp because of it. What is the problem & how long will it take to heal?