Good Evening, Ulcers can have various causes or sometimes no apparent cause at all. Many over the counter gels available help in quick relief from pain and promote healing of the ulcer.
Next Steps
If its a one off thing, you can use an over the counter gel like, Hexigel or Dentogel or Mucopain gel, applied twice a day to the affected area and avoid eating or drinking anything for 30 mins post application. However if you're having more than one ulcers at one site or more than one site and/or if the ulcers recur often, I would suggest you see your dentist and rule out any particular cause and/ or get treatment for whatever might be causing the ulcer, for eg: a sharp tooth for the ulcer.
Health Tips
If the ulcer does not heal with application of one of the gels within 2 - 3 weeks, please see a dentist irrespective of the size , number or location of the ulcer.