Sounds like impingement of cartilage between the medial malleolus and the medial facet of the talus. - a piece of cartilage tear stuck there. Might show on MRI and needs debridement surgery though I have tried cortisone injection into spot...

Van Dijk, C. N., P. M. M. Bossuyt, and R. K. Marti. "Medial ankle pain after lateral ligament rupture." The Journal of bone and joint surgery. British volume 78.4 (1996): 562-567.
Bone & Joint


You need to see an orthopedic surgeon that specializes in ankles.