Hello,
From the picture it looks like a canker sore. Avoid spicy or acidic foods during this time.You can use topical ointments like numbing ointments, such as benzocaine (Oragel), anti-inflammatory (steroid) gels,benadryl allergy liquid mouthwash,oral preparations of steroids and vitamin supplements.
But if the sores last for more than 3 wks or start spreading then pls consult a dermatologist. In that case herpes simplex I has to be ruled out.
Hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional queries.Kind regards.
You do not kiss your way to an infection overnight.Fits in with an aphthous stomatitis.Bcomplex should help.