Ankle swelling or leg and foot swelling (Pedal edema) due to cardiac, renal or
liver diseases is usually bilateral i.e in both legs/feet/ ankles.
Swelling (pedal edema) on just one side may be due to local trauma/injury, cyst, venous causes, DVT, infection,etc.
I am sure your treating orthopaedician must have ruled out these differentials.
( In Infection there may be some redness over the swelling/ warmth over the swelling/ discharge/ pus/ sinus/ fever/ tachycardia, etc
In DVT there may be tenderness over the calf,history of long travel or prolonged immobilisation/ history of blood disorders, etc)
From the clinical photo provided it looks more like a bursitis or a cyst.
Next Steps
Looking at the age its always better to get a routine check up done by a physician(M.D Medicine)
For the ankle swelling:
Rest, ice fomentation, elevation with 2-3 pillows.
Crepe bandage may be used while walking or standing but care must be taken that it's not too tight or not applied for too long.
If no improvement in 2 week- USG Right ankle
Health Tips
(note: this opinion is based on the limited information provided in the query and is not a substitute for physical examination and consultation. It's advised to consult a doctor in person)