You sound pretty freaked out by this.
I thought of something funny - You are not a black belt in karate or anything!! I know that was dumb it just made me laugh.
I am only guessing at what has caused it first. Is the band around your waste - Does it match the band of where your trousers may sit?
Because if you can work out what may be causing the irritation you will be half way there.
If it is around your belt area - Do you tuck your shirt in or leave it out. Just thinking whether it is something irritating your skin from the pants or something tucked in.
The colour may not impress you right now but don't do anything that may aggravate the already aggravated skin. Keep it well moisturised with a balm or salve or something.
The colour is not the problem right now - finding the source of the irritation is!!!! If you do not it may spread on you and that is definitely not going to make you happy hey.
Look forward to hearing that your problem is soon solved. Good luck. Don't panic just investigate it.