Thanks for the query. Extremely difficult to give a specific diagnosis without looking at a picture of the lesions, but potential causes could be aphtous ulcers (canker
sores), herpetic ulcers (cold sore
inside the mouth), mucoid cysts, among others.
Indeed, you need to see a physician who can directly assess the lesions and determine if a diagnosis is possible just by inspection and history.
Dr Brenes-Salazar MD
Mayo Clinic MN