Jul 18, · Complications of canker sores If your canker sore is left untreated for a few weeks or more, you may experience other, more serious complications, such as: discomfort or pain while talking. Cold sores have painful symptoms. Facial nerve pain after the herpes simplex virus (HSV-1) has been activated is less common, but it can occur.
Pain from a canker sore tends to get better in a few days, and the sores usually heal without treatment in about a week or two. Treatment for large, long-lasting, or unusually painful sores might.