Pain in knee and hamstring after squatting down on legs. i didn't move fast or hard. could i have torn something? or just stretched it too much?

A tear: usually results in SEVERE and IMMEDIATE pain .... (Often the person with a tear cannot get up from the squat!!) Probably a strain/sprain..ICE and consult your PCP is pain persists Hope this is helpful Dr Z

Sprain: This is likely from a sprain since you will have much more discomfort if any tendon is torn. One would expect that you will recover within a few weeks if just a sprained. If the pain persists or worsens, consult an ortho doctor

Possibly: It does not sound like a real mechanism of injury, so a major ligament or tendon injury would seem unlikely, however, there are occasions that the posterior portion of a meniscus can tear with minimal injury and cause pain in the area you are describing. Don't hesitate to be seen if it does not rapidly resolve.