Tell a parent or someone you trust. There is stuff over the counter you can buy like Monostat because if you go to the doctor they are probably going to want an exam, and I know you are still young and may not be comfortable with that. But, if over the counter stuff don't work you may need to see a doctor.
Tell your mom. I had them a lot when I was a kid. She will either take you to see the doctor or get some cream to rub around your no go zone. It's nothing to be scared about. But, tell you mom and see a doctor, because it could also be a UTI (urinary track infection).