How to treat a blister on my gums?

Gum blisters: Canker sores, also known as mouth ulcers or mouth blisters, appear on the tongue and gum. They usually heal on its own in about a week or two. If the sores continue to persist, or are large or painful, visit your dentist. Depending on the nature and severity of the sore, dentists prescribe antimicrobial mouth rinses, corticosteroid ointments, or a prescription to reduce the pain and irritation.

Canker sores: I've tried many things but this is what i've found most helpful: use natural toothpaste without sodium lauralates, take probiotics or yogurt, apply liquid seal like zilactin to protect from biting/irritating, avoid ones with pain killers like Benzocaine as it irritates more than any pain relief.