Hello,
Ulcers in the mouth are a common phenomenon yet there are a number of reasons why this condition might reccur. Usually it occurs during period of high stress, if there are any oral disturbances lik sharp edges on your tooth, harmonal changes and so on... You have to keep an observation regarding the cyclic pattern and if its occuring due to stress. U can apply dentogel over the area, keep urself hydrated and take
vitamin b complex tablets for 1 week.
If the problem is persisting or if there is increase in number of the ulcers do visit ur dentist for a proper examintation and with deatailed history