Yeah, it's from the skin on skin contact of "binding down;" I've had this happen as well, and it's pretty uncomfortable. There's nothing you can do about it but let the skin breath and use some powder when you do bind. This sucks with extreme dysphoria, but there's nothing else you can do if you can't get surgery now. If you don't tend to those areas, it can lead to rawness and semi-permanent pressure scarring, which I have also experienced. Hope that helps.
-Dom