I was doing yoga & suddenly got foot & knee pain. its been 2 weeks & still the pain is same. when i did standing stretching exercise, it got better.?

Hard to say: There are multiple potential causes and usually a detailed exam can determine the cause. It would seem a little unusual to have injured your knee and foot at the same time (although it is possible), so one cause might be a sciatica. In sciatica , a nerve can be irritated in the back and cause pain running from the knee to the foot. Consider being seen.