What Causes The Formation Of Knot Above The Ankle?

I've had a knot just under the skin just above my ankle for 4-6 wks now. There is redness around the site, but doesn't feel warm to the touch. Saw my PCP & he said some huge, long word that was possibility, but essentially blew me off. CBC, CMP all nml. The knot moves though...it doesn't feel like it's attached necessarily...but I could be wrong.