What Is The Treatment For Pain In The Knee And Ankle Of The Legs?

Hi. I have pain in the back of my L knee which radiates down my leg into my ankle. It is painful enough to notice the pain in sleep. If looking from the rear the pain is on the left rear side of my knee. Pain subsides when at 45 to 90 degree angle. Pain comes back sharply as I straighten my leg or put pressure on it to walk. There have been clicking/popping sounds on occasion but not everytime I straighten. I am 31F 5'6" 120lbs, had an ACL surgery on this at 16, but this pain is new as I've only had pain prior to this after strenous exercise (as in skiing all day). I did crash on my bicycle about a month ago and my knee was swollen a few days and the clicking started after this crash. There was no significant pain then. It's worsened now to this point, I think, because I'm a clutz and have actually banged my knee against a couple of other things since. I'm wondering if it's just sore? Or if I really need to get to a doctor. I'm uninsured. Thank you!