Help with Hanzel's lip & paw pad

We have 2 black & whites we rescued through ARWOB. Hanzel & Gretel, brother & sister both 10 months old. Hanzel Hirt his back right paw. We think on a protruding carpet nail strip. He also chewed on it. There were open sores around paw pads. Vet examined and did not find any splinter or object. Gave him Convenia, antibiotic shot and Dexamethasone, anti-inflammatory shot and we put a cone on him. Paw is scabbing up and healing. But now we noticed his lower lip was swollen and protruding. The next day it looked like a cold sore a human might get. Next day it seemed aittke bigger and also his gum has something going on. We're monitoring it and if it gets worse will take to vet after the holiday. Is this a viral thing? Will antibiotic help like Fish Mox that I've read on this site as an inexpensive & effective antibiotic. Any idea what this is? Not sure if what was happening to his paw somehow transferred to his lower lip? Any help and advice and possible treatment for Habzel is appreciated.

Also no signs of Gretel his sister having the "cold sore" on her. They eat, drink from same dish. Play and wrestle, groom each other.

This us Hanzel's lip today 7-5-15. Seems to be scabbing up. Lip still protruding but not as much. Paw is improving and looking much better as he had the cone on and cannot lick or chew on it. Thoughts on this current pic?

It looks like some kind of infection, but I can't say what. I really wouldn't advise you to try fishmox - you need to know the cause first, and it might interact adversely with the antibiotic shot he was given. Get him checked by a vet. The last thing you want is for the infection to spread further in his mouth and gums.