Stress is a common cause of these types of sores, but they can also be brought on by accidentally biting your mouth or eating certain foods. To keep them from forming, it is important to try and reduce stress as much as possible while staying away from anything spicy or acidic that may irritate the area more. Good oral hygiene will help prevent future outbreaks. Over-the-counter gels are available at most stores, which will numb the pain temporarily and speed up healing times. If none of this works or if they won’t seem to go away then please see a dermatologist/dentist for further assistance.