Hi.. Can understand your concern.. As per your complain it seems that you have Canker sore / apthous ulcer. There are many conditions considered as causative factor for occurrence of canker sores some commonly occurring are like allergic reaction, acid reflux,stomach upset, excessive intake of citrus food products etc but the exact reason is still unknown.. The treatment is based on relieving the symptoms.. For relief from pain and inflammation Ibuprofen can be taken as it will control inflammation and relieve pain. Gargle using half milk of magnesia and half benadryl liquid. Warm saline gargles also provide relief. To prevent discomfort during food intake apply numbing gels like Mucopain gel or orabase gel half an hour before meals so that it numbs the area and reduces discomfort while taking food. Avoid hot and spicy food.. Avoid sour foods as they can exaggerate the symptoms as well as cause more sores. Drink plenty of water to avoid dryness of mouth which can further add up to the irritation. Hopefully the sore will subside in a weeks time but if there is no relief and the symptoms and number of sores increase you should consult an oral pathologist or a general physician. Hope your query is solved.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.