Hello.. It looks like you have mouth ulcer..even though the picture is not very clear.. First thing is have plenty of fluids.. Keep yourself hydrated.. Have tender coconut..you need to have green leafy vegetables and also consume buttermilk, milk etc..avoid spicy food.. Take b complex capsules once a day for a week,you can use zytee gel for pain relief three times a day before food...please consult a physician and get examined if symptoms don't subside