Brown rash exactly where my testicles lay in groin area, on both inner thighs. no itching. hygenic/not obese. what is this and how did i get it?

This can be a : fungal infection, bacterial infection, or postinflammatory hyperpigmentation, either wasy you should see a dermatologist for the correct diagnosis and treatment

Unsure, need to see: This rash would likely need to be examined and more history obtained to be able to provide you with useful input about the diagnosis or possible treatment.