Ok, one of my rats started bleeding earlier on his nail or paw (I would guess nail) and I don't know how it happened, but it seems to have stopped. I'm not sure if it's them fighting or not.
I'm not an expert by any means, but I would guess it's his nail/claw as well that was bleeding. Rat claws can break from whatever reason (I'm gonna say in your situation it's from rough play) and cause bleeding.
My two boys are only 2 and a half months old and they do the same thing. They play fight. I hear a squeak once in awhile, but I feel that that is normal rat talk telling the other to "back off". I agree with what ratsarecute said about the squeaking. If it sounds like a distressed squeak you should be worried.
I watched my rats extra carefully when they were doing whatever they were doing. One rat will sideways pin the other rat down and it looks as if he's "nibbling" or biting his skin close to his eye (which concerned me), but when I picked up the rat who was attacked, he seemed fine. No blood. And sometimes, both rats will rear up on their hind legs as much as they can go in their igloo and wrestle slightly. Another time, one rat climbed over the other right on top of his face and just lied there on the other rat's face. I usually have them separated unless I'm home, until I can figure out what they're doing.
And again I am not an expert, and I could be wrong, but I am gonna say by the description in this post that they are playing, because my two males are doing the same thing that you have described and it sounds playful. I have watch them closely enough to know that they are safe together and not really going to cause each other harm. They end their fights by grooming and then curling up to sleep again usually and that's that.
For now, if it makes you feel more comfortable you could continue to separate them the way you have been until you get a more for sure answer. But I'm feeling pretty positive that those two are playing. If you see more blood or wounds anywhere you should try to find a way to stop it or keep them apart.
Best of luck to you and your boys. I hope they figure out their little spats quickly.
