There are many reasons for pain and waking up with pain on both sides of the tongue when biting in bed. If you bite your tongue in bed frequently, it may be related to misaligned teeth or tooth decay or tooth remnants. Biting the tongue while sleeping may also be related to mental stress, excessive fatigue, poor sleep quality, and dreaming. Uncontrolled muscle chewing caused by nervous system disorders may also lead to tongue biting symptoms. If you suffer from cerebrovascular diseases, such as cerebral infarction or cerebral hemorrhage, you may also bite your tongue if you have poor fine motor skills, slowed speech or hemiplegia. If the symptoms are accompanied by limited movement of one side of the face, drooling, crooked mouth and slanted eyes, it may be related to facial neuritis. If you bite your tongue in your sleep and have a lot of pain, you should go to the hospital for examination and active treatment after determining the cause.