I Have A Weird Symptom. In The Throws Of Rem

I have a weird symptom. In the throws of rem sleep, I suddenly awake with a deep, terrible pain in the right rear quadrant of my tongue. I thought maybe I was biting it accidentally, but there is never an injury detected. This has happened about twenty times in the last year. The next day, there is no cut, but the tongue is sore. I have hashimotos thyroiditis, fibromyalgia, diabetes, and a host of problems that make my life pretty miserable, so I hope this is not serious. Thank you for your help.