Hello,
From the symptom it can be a fibroma, melanoma, Addison’s disease or a malignancy. I suggest you to get it evaluated from a dermatologist. A biopsy may be done to confirm the diagnosis.
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 dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
This would be something for a dentist to look at as he or she could determine if it was something inconsequential as a blood blister or a damaged taste bud versus a start of oral cancer. ...~MM