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A duration of 4 months is a long time. Simple lesions must have been cleared by this time.
It is a good thing that other joints are not involved and there are no systemic complaints.
The cause then must be local only
Considering your young age, one must aim to avoid long term deformity
or complication. The best option is to see an orthopaedic doctor. He alone can pinpoint the source of pain - nerve
, muscle, joint, ligament, or tendon. And give appropriate advice.
Wishing you speedy recovery