What Causes Swollen And Sensitive Skin In Vagina?

A few days ago I realized that I had a scratch on the skin between my anus and vaginal opening, that stung when it came in contact with water. I know have a swollen right labia, that has a similar feeling. It doesn't have blisters, but small red bumps. I have semi-sensitive skin, and tend to get hives when the weather changed or I scratch. I've had 2 sexual partners in the past 2 months, and neither of them have shown signs of anything similar. I'm confused on what it might be??