Hello,
If it is a fungal infection, it would not have remained confined to a single spot for so many years because fungal infections spread and transmit easily. Ringworm is a fungal skin infection that occurs on the face, body or scalp. The symptoms of Ringworm or Tinea Capitis include a dry itchy scalp, scaling, crusting, inflamed nodules, hair loss and tender enlarged lymph nodes on the neck. I suggest you to get an examination done from your doctor and get a KOH examination of the scrapings to check whether it is a fungal infection. Then treatment involves using topical and oral antifungals.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Are you sure it's a fungus ? If so try bathing it with bicarb soda, that kills the fungus in my husbands toes.