Does it have a smell to it? Abscesses can sometimes have a pungent scent. Not sure what it is, of course, Abscesses may not make the bunny act differently, hence why no real change in behavior. (though I wonder if the red spots are from your bunny licking it or biting it? ) IF it is infection, the inside stuff can attach to muscle and bone as abscesses grow larger making it more difficult for a vet to clean out. So best to try to get this resolved sooner than later. They don’t usually go away on their own. Vet care with antibiotics will be in order. But again — I have no idea if that really is what is happening. Just one scenario.
I know this is worrisome to you and I am sorry you and your bunny are going through this. Do you have a rabbit-savvy vet you already trust? If not, I can give you a link to some near you. I can message you directly with the list to keep your location private as well. (Since I am one of the admins, I am aware of your location and can provide with vet information in your area).