Hello
Thanks for writing to us.
The important possibilities which can present with such symptoms are :
1) Vitamin B complex deficiency- Taking appropriate supplements will help in recovery.
2) Gingivostomatitis which is an inflammation of the oral mucosa and gingiva is common in young adults and has prodromal symptoms (fever, malaise, irritability, headache, vomiting, lymphadenopathy) 1-2 days prior to local lesions after which lesions appear in the mouth forming small vesicles which rupture quickly, resulting in shallow, round, discrete ulcers with erythematous halo.
3) Aphthous ulcers in response to an infection
In gingivostomatitis, symptoms usually resolve with fluid intake, good oral hygiene and gentle debridement of the mouth. Use chlorhexidine mouth wash and avoid acid drinks, like fruit juices or fizzy drinks, or drink them through a straw so they don't irritate your mouth. Also avoid spicy food and sharp food and citrus fuits.

You can use topical ointments like numbing ointments, such as benzocaine (Oragel). Yes these are available over the counter. You can read nearby pharmacist at the pharmacy.

I hope my answer and recommendations are adequate and helpful. Waiting for your further follow up queries if any.
Regards.

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