My knee hurts when i put pressure on it. not when i run or bend it or anything else. just with pressure. what could be wrong with it?

INFLAMMATION: This sounds like mild inflammation of the supporting muscles and tendons of the patella ( kneecap). Many causes are possible:if you are exercising- remember to warm up and cool down. Certainly simple passive flexion and extension of the knee will strengthen the quadriceps and supporting ligaments. I suggest massage with biofreeze. If not improving-orthopedics.

Multitude.: Could be one of many possibilities. A Meniscus tear, possibly soft tissue inflammation around the kneecap, or the tracking of the kneecap. See a non-surgical sports medicine physician for evaluation.