My right knee is in a lot of pain.?

Im 16 and when i was about 13 i played soccer and during a soccer game i got kicked in the knee cap and my knee cap shifted. Ever since then i have had some off and on pain, but over the years it has progressed. I had a MRI a few months ago and the results were that i had a very very small tare and it wasn't a big deal, but now when i walk and extend my knee it hurts a lot to the point where i have to baby it and not extend it as i walk. should i go back to a doctor or should i just deal with the pain? please help me!