I feel tightness behind my knee and some pain in the inner side of my knee. my knee pops or cracks with each step i take. stairs hurt near patella.

Meniscus tear.: You may have a meniscus tear. See a sports medicine orthopedic knee surgeon for an exact diagnosis.

Hard to say: It is hard to give you an answer without a proper physical exam. Possible etiologies include inflammation of the joint, bursa or tendon. Try elevating and resting the knew for a few days - if the problem persists you need to see a physician.