I have a tiny rash on the inside of the case between my right leg and vagina. it only appeared a few days ago and it seems to sweat a bit during the day and it smells weird. i think it is just from the fl heat and sweating mixed with too tight of underwe

Yeast: This could be a yeast infection like jock itch. There are over the counter antifungal creams which can treat this, but if not improving should bw evaluated by your physician.

Fungal vs. chaffing: Sounds like you may have a dermatitis caused by rubbing, perhaps complicated by sweat and moisture and maybe a fungal element. Anywhere that is dark, hot, and moist can be susceptible to fungal infection. Abrasion or irritation from other causes can be complicated by a minor fungal infection. Keep clean, apply clotrimazole cream 2-3 times daily and keep the area aired out as much as possible.