What Causes Discoloration Of Foot Along With Pain In Ankle?

I sprain my ankle oct 9th,gradeII. It still aches with minimal swelling. I can tell one ligament might still not be healed. But my problem is that if I leave my foot still (dependent) for more than 5 minutes it starts a discoloration process to purple and in colder than my other foot. The EMG says that I have nerve damage but it appears to be the nerves on the outside of my calf and ankle. I have been to four weeks of therapy and I still can't build up my strength in my ankle of calf. Myt entire leg is smaller than the other. Could this be tarsal tunnel or something similar? Or what are the other possibilities? I am in my thirties and only have hypothyroidism.