Mouth Blister

I am a nineteen year old male. I have one blister in my mouth on the right anterior pillar. It hurts to swallow. What could be the cause of this? I have no other symptoms and I have never had this happen before. I woke up two days ago with pain in my throat. I assumed it was a sore throat but I noticed that it hurt near the back of my mouth instead of the actual throat. I have not done anything treat the pain except eat a tablespoon of honey before going to sleep.