Mouth ulcers can be caused due to many reasons but for symptomatic relief, you can apply Mucopain gel or Dologel CT which will act as a surface anaesthetic.
Next Steps
You need to visit a Oral Medicine or Oral Pathologist for a definitive diagnosis and management.
Health Tips
Please avoid hot, spicy food. Also use a Mouthwash like Rexidine plus or any other anti-bacterial mouthwash.