What to do if i have severe knee pain please help!?

Have knee evaluated: You should see a doctor and have the knee evaluated. Consider an orthopedist or rheumatologist.

Ice.: you can ice your knee , 20 minutes at a time, 3-4 times per day. If you can take an anti- inflammatory, like Advil or Aleve, (naproxen) that would be helpful. Most of all, you should see an orthopedic knee specialist, for evaluation.