flat lump

My rats tend to get lumps on their neck occasionally which are always abscesses that pop on their own. The reason for the lumps are unknown but I am trying to improve the cleanliness of their cage. About a month ago, Yoda formed an abscess under his chin and it opened just before I went on holiday. I asked my dad to wipe the area with saline solution until it healed as I usually do, and it was healed by the time I came back. A few days ago, I felt a tiny bump on his neck sort of like a small pimple or wart. I decided to just see whether it developed or not and today I saw that it was quite a flat but larger lump and I'm wondering if it didn't heal properly. I think it's worth giving him some antibiotics since I have lots left. Is there anything else I could do?

Abscesses around the neck can often be bite wounds. Do any of your rats scuffle or fight? It's possible that it's only a few abscess that keep recurring as well. It's best to flush them out twice a day with saline ..getting right in that cavity. If you don't flush them bacteria can remain inside as it heals over and sooner or later the abscess comes back.

Thank you so much, I suspect that's what happened. I don't actually see my rats fighting a lot but Chewie does seem to be the alpha. Although it's only just started developping, should I wait for it to grow and rupture, and meanwhile give him antibiotics? I don't think they need to be seperated but I'll keep an eye on them.