Hi
I think you have your ligaments torn in your ankle. Initially it was torn and you didn't give proper protection and rest so healing didn't take place properly and now this injury has aggravated the ligament tear.
Next Steps
RICE - Rest, ice, compression with crepe bandage and elevation till the swelling comes down then followed by walking cast for 3 weeks if you want proper healing and it shouldn't come back
Health Tips
Regards
Dr Sachin Jain
Arthroscopic surgeon and sports medicine expert, Jaipur