What Causes Pain In Thigh When Bending Knee?

I think I hurt my thigh/hamstring after one particular yoga practice a week ago. The thigh is not swollen but it is hard sometimes to bend my knee; it feels like there is a thick band squeezing the circumference of my thigh right above the knee. Did I pull my hamstring? I've iced it off and on and having been taking Ibuprofen prn.