Following could be possibilities,
1) Ankle sprain with ligament tear which might have healed properly
2) Post traumatic arthropathy
Next Steps
1) Detailed clinical examination
2) Investigations-X ray followed by MRI, if needed.
Health Tips
1) Ankle Joint Rom Exercises
2) Avoid ground level activities, walking on uneven surfaces
3) Contrast Bath-Cold pack*15 mins followed by warm packs*15 mins,3-4 times a day.