Infection and stress may also cause the sore spots in your mouth. Canker
sores or aphthous ulcers, are small
sores that occur inside the mouth and may also show up in small clusters. A small red bump rises and may bursts, leaving an open, shallow white or yellowish wound with a red border. The sores are often painful. Most canker sores will heal on their own in a few days to a couple of weeks. If it persists, have this evaluated further for proper management.