There isn't sufficient information to suggest a specific diagnosis. It is possible that it could be a fungal infection. I would advise you to meet a dermatologist so that you can be examined and undergo the necessary investigations(if required) to find the underlying cause and have it treated accordingly.

If it is not hurting and was gradual. It is likely to be fungal infection. Just local antifungal application and 5 days course of antifungal orally will do the needful. For local application you can use itraconazole and for oral intake fluconazole or ketoconazole can be taken twice daily for 5 days. Please check your thyroid, Grbs/ppbs/hba1c and keep a check on your respiratory system as well as to any breathlessness or chest pain if occurs anytime.