I have this stinging pain in my knee, everytime i extend it and bend. i did sprain my mcl before could this be because of that. if so how can i fix it?

Get it evaluated: First of all, you need to have the knee evaluated to determine the cause of the pain. An MRI may be needed. See an orthopedist.

Depends where : Where do you feel it? Front or back of the knee? Your diagnosis could be correct but we need more information. Is there swelling? Is there locking? Did you injure it? Do other joints hurt? Is it tender to touch? Where? This could be cartilage? This could be arthritis. I would be concerned that there is an internal problem and you need an evaluation.