Suggest Remedy For Painful Knee

I've been feeling pain in my knee and I'm not sure what to do. It started hurting about a week ago and after about 5 days it started to feel like normal. I would walk and forget I had even had a problem with it. It was like a muscle cramp around my knee (it started just the left of the knee cap and it went down to just below the cap).

As the pain went away on it's own I didn't see my doctor and went back to my normal routine. I did some gentle exercises and walking and the pains come back, not as bad as before but enough for me to notice. Is there anything I can do to help heal my muscles?