This is a good question. It is very important that you make an appointment with your primary care doctor
or ob/gyn as soon as possible to have a full history and physical and testing, if needed. A rash on the fold between your leg and genital area that has a slight odor could be yeast, especially if it is itchy. This can be caused by dampness, such as by wearing sweaty workout clothes or wearing a wet bathing suit. Another possibility that you always need to consider if you are sexually active is sexually transmitted diseases, or STDs. Syphilis, for example, can present with a rash so be sure to mention your sexual history to your doctor. Another possibility is an allergic reaction to something your skin was exposed to in that area, such as a new pair of underwear. This is called contact dermatitis and it usually presents as an itchy red bumpy rash. Again, it is very important to seek care with your primary care doctor or ob/gyn to determine the correct diagnosis and get appropriate treatment. In the meantime, try to leave the rash alone - do not pick or scratch as this can lead to infection and scarring.