Apply a plain yogurt compress on the skin by smearing the yogurt on one side of a cloth and placing it on the rash for about half an hour to sooth and cool the rash. Put a few drops of tea tree oil in your moisturizer every day.
Over the counter Hydrocortisone cream should help the rash. A yeast rash will respond fairly quickly to hydocotisone and the ability to keep the area dry. Warm moist skin is a breeding ground for yeast infections.