I’m sorry to hear what is going on.
I lost my own bunny Peanut to pretty much this exact same thing. Instead, he had a broken tooth that caused the abscess under the chin.
So far, it sounds like you shouldn’t be too concerned, considering the packing could probably move around. (maybe I’m mistaken, but I’ve never had that done to my own bunny) In fact, whenever I felt Peanut’s abscess after surgery it felt hard like you’re explaining, and for his length of time he was still here it always was like that, just a small little place that fur started growing around. I’m not sure if the packed antibiotics is different than what Peanut had, where we just let his abscess site drain. But so far it sounds rather normal. I suggest you keep a very, very close eye on your bun, make sure he’s (or she, sorry but I don’t see a place where you signified the gender) acting normal, eating hay and pellets or whatever you might feed him. If he’s acting mopey and lethargic, it might mean he needs the abscess drained again and his teeth examined for more broken/loose ones.
If things keep getting worse, I’ll see if I can find you the website where my mom found a cure for this sort of thing if an infection may occur. Just let me know and I’m happy to help!