Could likely be CRPS

"Physical therapy and cognitive-behavioral treatment for complex regional pain syndromes"
https://www.cebp.nl/media/m1063.pdf

Just an article you may want to read. If you need any help with parts of it let me know! Just to clarify, you are doing exercises/stretches for your ankle already yea? Sometimes simple steps (i.e. proper rehab) can be missed completely. Could you give us an idea of the things you are currently doing? And maybe we can give further advice.

Thanks, good luck!