I Have Strong Pain On The Outside Of My Knee

I have strong pain on the outside of my knee and it hurts to bend or straighten it. Also I can press the exact spot of the pain. What should I do for it and what might it be? It came just today and is getting worse by the hour. I did fall on my knee a few months ago and couldn't and it was very painful and I couldn't kneel on it for at least 2 months but that has gotten better and now this extreme pain on the outside of the same knee!