Lump from a bite or tumor?

Hi,

I have three female rats all living together. Two days ago, I noticed one had a bite wound right at her bottom-most nipple. She is just over a year old, but probably the largest female I've ever seen. A bit fat, but mostly just large bodied.
Anyway, the wound has pretty much healed, but when I was checking today, I noticed a round lump right near the bite scab under the skin. I don't think this was there before the bite, but it's a small enough lump that I could have easily missed it. I know this could either be a tumor or a case of the surface of the wound healing and encapsulating some infection deeper within.

My question is, how fast should I expect to notice growth if it's a tumor, so I know to take her to the vet?
I'm keeping an eye out for signs of infection, but she seems fine. Right now I'm hoping it's an encapsulated infection so her body can eventually break it down on its own.

I would include a pic, but you can barely even see the lump in real life. No signs of lumps anywhere else on her.

I think that after 2 days it is more likely a cyst or scar tissue. You didn't notice it before the wound?

That could be an abscess due to the bite. I would do warm compresses daily and see if it pops. At which time you would squeeze out all the pus and keep flushing the cavity to help it heal. Don't put any ointment on it.
How old is she?

Any changes?

I've been doing the warm compresses but no change. I didn't notice the lump till the day after the bite, and I feel like I would have noticed it when I was checking the wound...
She still seems to feel fine though

Ok good so it hasn't grown then. It's probably just normal scar tissue forming. Just keep an eye on it.

I agree, the fact that it's not grown is a good thing.