Hello, The posterior of the tongue could feel pressure from inflammation in the throat. With repeat episodes this could be viral in nature. Take some Antiinflammitory medication such as Tylenol or Advil to reduce symptoms. Look for initial signs such as a tingle. There are antiviral medications that can be effective if taken at early onset. Check if there is any type of ulcerated lesion. Stress can induce an episode. Track your diet or any change in products used. An allergic reaction is another possibility. While sleeping you may aggravate the side of your tongue with rubbing or dehydration that causes a sharp pain even if you don t see an actual bite mark. Your dentist can visually check for lesions or growths. The back side of the tongue is an area at higher risk for oral cancer, so seeing your dentist is a recommended choice to confirm that nothing new is now visible. There are blood vessels and salvia ducts that can also be visually checked. Consider having blood tests to check for any systemic disorders. A neurogist could be consulted if the condition persists without any possible diagnosis. Thank you for your inquiry. I hope that my suggestions are helpful.