Thanks for the query.
you might be suffering from a fungal infection
The other possibility is single plaque psoriasis
Treatment with oral and topical anti fungals may give you a good result.
might be required for a closer diagnosis.
Please meet a dermatologist
and discuss regarding this.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.