How To Cure Itching And Stinging Sensation In Vagina?

Hello. Our 6 year old was in great discomfort last night saying that her vagina was stinging and itchy. I could see nothing on the outer areas and not much inside either. We bathed her, dried her well and applied Vaseline. She was still in a lot of discomfort and it took about 1.5 hours for her to fall asleep despite her obvious fatigue.She also mentioned that at times she feels as though she needs to urinate but that nothing happens when she goes to the bathroom to pee.Any thoughts about what might be going on?Many thanks, Nikki