Ulcer in back of throat. not swollen and very little pain. no fever either. i threw up about a week ago so im wondering if the acid caused it? strep?

Ulcer: More likely an ulcer from some viral infection. Best way to is to have someone take a look at it, especially if persisting and not going away or changing after 10 10 14 days.

Canker sore: It may be due to a weakness in your immune system (e.g. flu). Your physician may prescribe an antimicrobial mouth rinse corticosteroid ointment to control the pain and irritation.