I was thinking maybe your wisdom teeth were starting to pop up early in your life which may cause pain in that back area.
Otherwise, the blisters may be what's causing the pain. It could be a cold sore or canker sore. You may want to see your dentist to get it checked out though.
This is caused due to tooth sensitivity. Tooth sensitivity is tooth discomfort in one or more teeth that is triggered by hot, cold, sweet or sour foods and drinks, or even by breathing cold air. The pain can be sharp, sudden, and deep into the nerve endings of your teeth.
There are some common ways these nerve endings can be exposed are through everyday use, traumatic injuries resulting in chips and fractures, untreated gum disease, brushing too hard or using a hard bristled tooth brush.
Apart from this, the blisters are may be cause due allergy for that you must visit your dentist.
I will suggest you to use sensitive toothpaste as your teethes are super sensitive type.