Yesterday my knew became swollen and still swollen today. but i have no pain and i can still move my knee around but feeling of pressure.

Ice the knee: Till you can see your doctor elevate and rest it. You could have strained or twisted it possibly.

"water" on the knee: A painless swollen knee is probably from a build up of fluid in the knee. This can occur from minor trauma, arthritis, or an infection. If the swelling does not improve, see your doctor for testing.

Most common Sprain: Acute onset at your age causing swelling and no pain is usually caused by a sprain. Apply cold compress and try few days of aleve (naproxen) twice a day, if not getting better in few days see your doctor, to rule out other possibilities