Mouth ulcers if occuring repeatedly could be a matter of concern. Recurrent aphthous stomatitis needs to be ruled out. Other causes for oral ulcers could be Oral Pemphigus, Oral Lichen planus, traumatic , due to raised acidity in your stomach, drug reaction etc...
Proper evaluation is required for better mangement.
Next Steps
Consult online for futher detailed evaluation so that best possible treatment can be given according to your specific problem.