Groin area is quite prone for fungal infections, intertrigo ,erythrasma. Sometimes seborrheic dermatitis
, inverse psoriasis
, pityriasis versicolor may also mimic such infections in groin.
Erythrasma or fungal infections usually heal in two to three weeks with adequate medication. The medications that you took were good enough to treat erythrasma.
I would like you to consult a dermatologist
, to rule out three possibilities
1)if there is a persisting infection fungal or erythrasma
2) if it is some other disease that you misdiagnosed as erythrasma
3) if the lesion actually healed and its only the pigmentation that is persisting.
If its only the pigmentation that is persisting, keeping the area dry and application of pigmentation reducing agents like Kojic acid
Hope that answers your query. Take care.