There Is A Bump Right Over My Left Knee Towards

There is a bump right over my left knee towards the inside of it. It is about the size of a dime, and every time I push it it feels like an air bubble or maybe filled with liquid, but as I push it, it leaves... It will stay gone for a few hours but will eventually come back... There isn't any pain until I touch the bump but it isn't an unbearable pain. Can you please help, I can send a pic if needed and a video