Landed on my left leg wrong playing volleyball and heard a pop in my knee. How can i heal it?

I went to spike the volleyball and landed on my left leg. I heard my knee pop, but kept on playing on it. It has been two months since the incident but i still feel pain when doing certain things. I cannot straighten or bend my left leg as much as my right leg and when i do this it feels tight. I feel pain when doing physical movements like squatting, jumping and sprinting. I still jog and lift weights but i want my left knee to be 100% again. How can i heal my knee without a doctor?