What should i do if i have this blisterthing on the end of my mouth what could it be from?

Cold sore: The most common form of problem at that location is called a "cold sore", usually of unknown origin. Rarely it could be viral like herpes. If persistent or recurrent, a dentist is a good professional to evaluate and treat this.

Blister: As with most questions here, seeing a professional is always advisable, in this case your dentist. You didnt describe how many blisters, size, duration, what happened prior to their arrival etc, lots of unknowns, see a dentist, may be nothing,( ie will go away in a couple days) or be something which warrants further investigation...

Canker sores: Most mouth ulcers, canker sores, will clear up by themselves within a week or two. You should see your GP or dentist if the ulcer gets worse or lasts for longer than 2 weeks. Take care.

Cold sore: The most common form of problem at that location is called a "cold sore", usually of unknown origin. Rarely it could be viral like herpes. If persistent or recurrent, a dentist is a good professional to evaluate and treat this.