you sprained your knee.
DO NOT take anti inflammatories, you can cause more damage to your knee if you do.
I would ice it down and alternate heat. a doctor will probably do Xrays (which 99% you don't have anything broken) and an MRI.. (very expensive) all to diagnose you with a sprained knee. is it worth the cost? that is up to you, depends on insurance. I myself wouldn't bother going to the doctor over a sprained knee. the only thing you can do is rest it and grab a bottle of n2jointrx right now. all the doctor will do is tell you to rest it and give you some drugs for inflammation and pain, they are NOT trained to help athletes.
really in this situation the only positive thing you will get out of the doctor is a referal to a PT, what you need to do right now is research good physical therapists near you so you can request it. they will help you recover faster from your injury. sprains take a long time to heal and the first few weeks are critical.