I Have A 62year Old Ureterostomy Scar And 2 Days

I have a 62year old ureterostomy scar and 2 days ago what looked like a boil formed, I've been keeping it clean and using newsprint and covering it. It seems to be getting smaller and the red is fading. Why would this happen? That part of my skin wasn't damaged or anything and its always covered. Would you have some explanation? This is the first time anything has appeared on my skin. Thanking you for you time.