In the past few weeks, I have learned important things about my right knee. There are only a certain amount of pain-free steps it can take. The pain-free steps never come when you are first walking on it. Once it’s done taking those pain-free steps, it will get even with you for taking them. Oh, how it will get even.
There is a certain kind of pain that my right knee can toss off that isn’t very strong, like half a shitty menstrual cramp, a quarter of what a migraine can do to me, a flavor of pain you’d barely qualify as pain, really. I mean, it’s about on par, if not a little less than a stubbed toe. And my knee doesn’t have this pain very often, mostly when I haven’t moved it in a while, but, when it comes, I can taste metal in my mouth and it makes me so nauseous.
Of all the pains my knee has taught me about, this one scares me the worst, because all the other pains feel like “pulled something,” “strained something compensating for the pulled something,” “something’s tender right there.” The almost painless pain that makes me want to throw up from the taste of it? It feels like a wiring problem, like I have done something to a nerve in the knee. I also suspect this because it is usually accompanied by a feeling like the front of my shin, down by my ankle, is burning.
It feels like the kind of ugly pain that might not leave even after everything is fine.
Tiny Cat Pants 
What you are describing sounds like it’s almost certainly nerve pain. See your physician ASAP. You will probably be told you need an MRI — get it ASAP.
While they are figuring it out, they may be able to give you medicine that deals with the pain. But don’t put off dealing with the actual problem, because nerve issues tend to get worse and not better. The good news is that there’s often a fairly simple, physical therapy fix.
I was going to suggest having it massaged by a professional. My knee’s been bothering me off and on since I took a bad fall some months ago. I finally asked my massage therapist to work on it and her reaction was priceless. Apparently my knee is totally messed up – the other one is not. She worked it pretty hard that day and it’s been more or less fine ever since. Now I know where to massage it, too, so I can do it myself.