I have a rash in my inner thigh. Somewhat itchy. Just came up overnight?

Intertrigo. The two prescriptions that are effective for intertrigo are alcortin a and vytone cream 1%. See you doctor for a prescription.
Jock itch? The most likely diagnosis is probably jock itch, but without looking at it I can't tell you for sure. Try an otc antifungal cream, and if it doesn't help, let a dermatologist have a look at it.