Thanks for asking the query,
Soreness in the mouth can be due to infection in the anterior tooth, allergy
to some food stuffs, nutritional deficiencies.
I would suggest you to visit to an Oral Surgeon and get the thorough checkup done, take an OPG radiograph which will give the exact diagnosis and treatment plan.
Apply Dologel oral ointment topically over the affected area.
Take lukewarm saline and antiseptic mouthwash rinses.
Hope this helps out.