Hi. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.... As per your complain it seems that you have a MAJOR APTHOUS ULCER [MAJOR APTHAE] which is a type of apthous ulcer or canker sore but it is larger than 10mm in diameter.. It can be caused due to a number of reasons like Nutritional deficiency[Vitamin B12,iron and folic acid],stress, GERD, uncontrolled diabetes, HIV,radiation and chemotherapy,physical trauma like injury with sharp edges of teeth etc.. It can take from weeks to months to resolve and can also leave some scar while healing .. The treatment is planned towards reducing the discomfort and initiating healing.. You need to take a Steroid dosage in tapering dose like Prednisone 10 mg twice a day for 5 days,followed by half a tablet for next three days and then half tablet once daily for two days ,A multivitamin tablet like Zincovit has to be taken for a month and in case of pain Ibuprofen or tylenol can be taken.. Apply a numbing gel like Lignocaine gel over the ulcer for relief from pain and discomfort especially during eating.. Apply a steroid based oral paste for reducing inflammation.. Sucking ice pops can help.. Gargle with warm saline and 1:1 solution of benadryl and milk of magnesia can help.. Avoid hot and spicy food.. You should continue the treatment for 10 days and in case if the healing progresses then it is fine otherwise consult an Oral Physician and get evaluated and a Biopsy can be required to rule out the exact cause of the lesion as a persistent ulcer on tongue can also be a malignancy.. Hope this information helps.. If you find the answer helpful please give me a Five Star Review and click on found the answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora..