Well, I'd try not to analyze your labia so much. :>) I get it, you want to have good reproductive health. The likelihood is that all is fine. No std's are related to change in color and size of your labia. Hormones usually change that. Shifts in hormones.
The rash. Well, not sure. The surface can be bumpy. It can be hair follicles even (yes, ON your labia). Have you always investigated the area this closely? You are talking about white bumps on the whole labia? Do you have itching or discharge?
What about this? https://www.webmd.com/skin-problems-and-treatments/molluscum-contagiosum That's a skin thing that can happen on your genitals and cause bumps.
So, I'm glad you have some regrets because that will inspire you to either abstain next time or to use a condom for sure. This is best practice, one of those two options. A pregnancy test may be in order as well if you had unprotected sex.
Do you live in the United States? They have Planned Parenthood here where girls that are under age can come and receive care for small fees. You would not need your parent's consent.
Otherwise, you can observe it. Don't douche or anything like that but wash with a clean washcloth. Keep it clean and pat dry. Try not to keep poking around too much (and remember, your fingers contain bacteria. Never pick at a sore on your genitals as that in itself can cause an infection). If it continues, you are going to have to see a doctor. How old are you by the way?