Dear friend, welcome to HCM!
Do you also have fever, chills
Is the overlying skin normal or reddened, has a cap ?
It appears to be an infected boil, or worse an abscess
Watch for fever, rapid increase in size etc.
See a surgeon if these occur and start antibiotics if fever starts.
Oral OTC cloxacillin
, if available, can be considered till you see a doctor (500 mg 4 times a day)
Take care and please keep me informed of your progress.
I hope to have answered your query satisfactorily.