Cannot tell without further examination. Sure it is abnormal for a sore to be present for 3 months. If your doctor suspects it could be something unusual, he would biopsy the sore and send it to the pathology department for examination. Only this would give answers to your question.
That would certainly be possible, but it could also be other condition, such as pemphigus foliaceus, bacterial infections or just bad weather. You may need to see a doctor to find out.