Hello, Mouth ulcers are very common occurrence. Although painful most of them heal in 4-5 days duration depending on the size &  location of ulcer without any medication. For symptomatic relief one can apply lignocaine containing ointments available over the counter. One should look into cause of ulcer if it occurs frequently. Common causes include indigestion, trauma, stress... If they persist for more than 5 days, then please visit your dentist to find out the cause &  to receive appropriate treatment.. Hope this helps.. Regards, Dr Vishank Shah