Having blisters under the tongue can be a symptom of multiple causes, according to WebMD. Since some tongue problems can be dangerous when left untreated, if the blisters remain after one to two weeks, it's best to see a doctor.
Canker sores are a common tongue problem that are notorious for causing bumps or other inflammations of the gums. They can frequently hurt a lot. These mouth ulcers tend to get worse under periods of personal stress.
Enlarged papillae can also be the culprit. These protuberances on the top of the tongue contain the taste buds. Inflamed or irritated taste buds can lead to painful bumps on the tongue.