What Causes Swelling And Blisters On Vagina After Intercourse?

I recently had sex and my vagina is very sore .. It s a bruised swollen kind of feeling .. However I went to look with a mirror and spotted a white blister look alike spot on the inside of my vagina.. I simply just wiped it off but it hurts when I go to the bathroom .. What could that spot be ? Should I be worried?