This most commonly looks like a traumatic ulcer or aphthous ulcer, especially since it is painful on touch and present for a few days. It is usually caused by accidental bite, sharp tooth edge, or irritation. Maintain oral hygiene, avoid spicy/hot foods, and use a topical ulcer gel. If it does not heal within 10–14 days or increases in size, get it examined by a dentist for confirmation.

Hello. Nothing to worry.it looks like ulcer.

Hello It doesn’t look anything dangerous

You may apply honey on affected area .

Hello Nothing looks serious