I would treat it just as a regular ankle sprain. The casting has added to your recovery time by sensitizing the tissue, maintaining the oedema, weakening your soft tissues and reducing your mobility. Circulatory problems and discolouration are common post sprain and post casting but generally improve with massage, modalities (ultrasound etc) and mobility exercises. You should ideally seek a physio with manual therapy training and experience working with athletes. Good luck. Marj