You might have got ulcers because of some food allergy or some deficiency. Have you applied anything on the ulcer ? If not you can apply any antibiotic gel meant for the ulcers on the them . After the application of the gel do not eat or drink anything for Atleast half an hour and no gargling either.
Next Steps
take folic acid tablet twice a day after food.
Health Tips
if there is continuous occurrence of aphthous ulcers, I would advice you to refer to a dentist to detect the underlying cause of the ulcers.