Thank you for your query at DoctorSpring.com
I have read your query with diligence.
It looks from your details you may be suffering from synovitis knee.There may be inflammation of covering of knee.This may be due to trauma.You should avoid heavy activities.Take mild analgesic like Advil for few days..Do cold fomentation. If there is fever then please consult to your doctor and have complete investigation.
Hope this will help you.