How To Treat Knee Pain Above The Knee Cap After Physical Activity?

My knee has been bothering me ever since I played volleyball last Wednesday. It is hard to bend after i have been resting for a while. most of the dull pain is on the backside of my knee, but above my knee cap also hurts at times. It almost feels like there is fluid on the backside, but there is no visible swelling. It has gotten worse every day.