What Is The Remedy For Canker Sore?

I had sex 4 days ago 6 times for the first time in 8 months, after intercourse i went to go pee and it sting real bad and it's been doing that ever since. I went to go look at it in the magnifying mirror and found a canker sore like at the back end of my vagina, I know this could be a tear due to excessive sex but how long will this take to heal? What steps should I do