Huge canker sore, what to do!?

Laser. Find a dentist with alaser wo knows how too treat these. Relief can come in minutes.
Canker sore. There are many otc medications that you can apply. Ask your local pharmacist what he\she recommends. If that is not enough to keep you comfortable, see you local dentist who can prescribe and\or treat this more effectively. Most patients just wait it out. Avoid spicy and acidic foods meanwhile.