I t seems that you may be having soft tissue infection
of the sole near ankle.
It may be due to bacteria mostly staphylococci contracted in walking at or in lake.
The area affected may be swollen and erythematous. There may be pain and tenderness. Area may be hot.
You consult nearby dermatologist
You should be investigated to rule out DM,HIV
or other immunocompromised. Conditions.
Oral strong antibiotics may be taken for about 2 weeks.
Anti inflammatory drugs may taken.
Immunoboosters may taken to improve immunity.
Hygiene may be improved.
Take bed rest
for few days and keep the affected foot elevated.
I hope you got my answer.
Dr. Ilyas Patel MD