Rat has gash on his back

Question
Okay I had two new rats, one(Mister) got very very sick so I took him to a vet.  When I got home from the vet Mister was dead.  Well my partner and I have been talking about the other rat(named 86) -how he didn't need to be a lone.  Well she decided to suprise me with a new baby rat (knowing nothing about them)
While I was at work she had 86 and the new guy on the floor and they got unto a bad fight.

*The new guy now has a deep gash in the middle of his back.  He seems fine, we have been putting meds on it and it is not bleeding, but it is just soo deep you can see everything!  
Do you think he will be fine?
Should I take him to the vet (My vet said he would see my other rat for free because of what happened to the first one.. I just do not want to take the chances.)

Answer
If the gash doesn't smell funny, isn't changing odd colors, going pus-y or weepy, or bleeding; you've done what you can for now, I'd sit back and see how it heals. If it begins to look infected in any way, you'll need to get him started on some oral antibiotics, but until then I see nothing wrong with waiting to see if that's even necessary. Good luck!