Hi I have similar feelings in my feet on and off it seems to move around. I have had all kinds of test but they never find anything. I think it may have something to do with stress, or stress on the nerves in the bottom of the feet. Nerves in the feet are the most sensitive because there so far from there "food source". I would not worry a whole lot unless it spreads. I hope this helps.
I also get the "tingling", but it's more like electrical impulse, under my large toe and heel of my left foot and on my knee of my left leg. They are so intense, my toe and knee almost feels as those they are being twisted off!! Other times my 3rd and 4th toes of the same foot will stiffen up and have the same electrical impulses, and I cannot bend them. It does not feel like a spasm or 'charley horse'.
My tests have ruled out MS, so now I don't know what the heck is going on. I do have neuropathy in my feet, so maybe that has something to with it, but what about the knee??