Hi there. Is it possible for you to upload a clear digital photograph of this balck spot using the upload data icon to the right of your screen onto this website. This will help us greatly as dermatology is after all a visual field! You definitely DO NOt have oral cancer & no-one will be able to diagnose this on a visual examination alone. Besides, oral cancer is NOT an infection. Yes..by all means, do give up your tobacco chewing habit irrespective of the outcome. Please visit your dermatologist closest to you. A skin biopsy from the site may help clinch the dioagnosis or it may just require a clinical trial with a systemic antifungal as per the doctor s view point. Do fel free to use our premier ask-a-specialist package & get in touch with us directly. Wish you continued good health & hope this has helped you decide the next course of action. Cheers & Good Luck! Dr Praveen Rodrigues MD Dermatologist, Cosmetologist, Venereologist Vikram Hospital, Bangalore, India