Abscess or eye infection or something else?

Hi! My hairless rat suddenly got this hard lump under his eye a few days ago. I separated him from my other rats because he likes to start fights & it gets him hurt too easily. My initial thought is that this is an abscess but it hasn't popped yet. I haven’t seen pics online of an abscess in the same spot so I am wondering if it is something else to do with his eye- like an infection? He can open and close his eye and it seems like the lump isn’t directly connected to his eye.. He’s had an eye infection before that gave him a bunch of gunk in his eye but this is just a lump. I have him on amoxicillin, warm compresses, and saline eye drops. I was giving him ibuprofen but idk if i should keep giving that because he doesn’t seem to be in pain right now, he's hopping around all happy. I can take him to vet if its necessary, just trying to treat at home if its something that can be treated. Thanks for your help, just trying to make him feel better!