People are continuing training with knee pops, torn meniscii and MCL?? You guys are nuts.
One of the biggest dangers of knee injuries is that your healthy knee starts to take more of a work load than your other one because you are compensating for the lack of strength/support on your injured leg. Since your non injured leg is now doing the work of two, the chance of injuring that leg due to muscle imbalances grows. That's why you see people who blow out 1 knee, then the other in succession.
Not to mention, since you're favoring your leg that is not injured, your currently injured leg muscles in your injured leg are in a state of atrophy. The muscle structure surrounding your ligaments get weaker, and instead of only having a sprained MCL, the next time you try and explosively use your injured knee that you think is healed, you will now rip your meniscus, your ACL, and PCL depending on which one is weakest.
Long story short, go see a doctor. If you don't like your doc's opinion, go get a second one. But don't keep training. At the very least go see a physical therapist.
If it requires surgery, go ahead and get it. Then just work on your rehab hard so that you get as much range of motion back as possible.
One of the smartest posts in this thread so far. Your rehab work and whether you take it seriously or not dictates how well your knee recovers. I sprained my MCL and my physical therapist kicked my ass for 8 weeks. I thought I had strong legs prior to seeing her. I dreaded the work outs but in the end BOTH my knees are stronger than they have been. The great thing is you can keep doing the work outs you learn to further bullet proof your knees!