Hi Bhavya,
Management of runner's knee mainly depends on the extent of injury and the underlying cause. In acute state give complete rest and avoid all those activities which can aggravate pain. Apply ice to reduce pain and inflammation. Once pain subsides you can start with exercise. I will advise you to start with open kinematic chain or low impact exercises like swimming, static cycling, isometric knee exercises, straight leg raises etc. Concentrate more on strengthening of inner thigh muscles especially vastus medialis. Include proper warm up and cool down with stretching exercises for the tight muscles especially of hamstrings and calf muscles. If there is patellar mal-tracking, use brace in initial stage.