It is also called canker sores that are small lesions or ulcers on the soft tissues of the mouth or at the base of the gums. Its cause is uncertain but can be triggered by multiple factors such as stress, injury in mouth, a part of illness or nutritional deficiencies. Aphthous stomatitis, or its lesions or ulcers often occur periodically and repeatedly.
Symptoms include whitish/yellowish round-shaped lesions/ulcers with a reddish border. They may be located anywhere inside of mouth, often found on the tongue, inside the cheeks, gums, or on the lips.
It usually heals itself. Please go to see your doctor if there is a severe pain or an underlying condition.