Bite Mark or Abscess?

I noticed Milo had a slightly swollen lip yesterday, but thought he may have bumped into something because they had all been very rowdy that morning. [Ever try to sleep thru morning veggies? Not happening!] Well, this morning all was fine, I had just looked at Milo and everyone was normal, I came back 10 minutes later and Milo had a bloody spot! None of my other boys have a mark on them, so I'm not sure if this is a bite mark, a busted abscess or perhaps he just ran into the brick in the cage.

Does anyone know what it might be? Of course, how should I go about making sure it heals properly and avoid infections? I plan on emailing the pictures to my uncle/vet to see if Milo needs to be seen.