I'm honestly not sure, though your desxription doesn't remind me of anything serious. Now that the urologists have ruled out internal problems, I suggest you consult a dermatologist, since you have a visible rash. Meantime, apply over-the-counter 1% hydorocortisone twice daily, keep the area lubricated, and don't rub or poke the area until you see the skin doctor.
Best.
Dr. Rockoff