Thank you Sam,
That was the key to our approach for this lad. The reason is because if the penis swells to a point that it cannot be retracted, that is an emergency situation for them. Otherwise, how to medically manage his wound does depend on how severe it is. Ideally, if there is swelling that could occlude the urethra and prevent urination, we'd want him to be seen urgently so that rat safe anti-inflammatories could be dispensed. Antibiotics would be prudent to use as well since the wound is likely infected (having come from another rat, though he will surely lick it as well). That said, if we had no swelling, then you could choose to topically cleanse the area with a mild antiseptic (ie salt water, dilute chlorohexidine) and monitor for 24 hours to see if it does settle on its own. Still if we have swelling and a wound severe enough to cause blood loss, then it'd be ideal to have him assessed at this stage.
Turning our attentions to the more behavior based issue for these rats, the disharmony in the group. In this situation, you have two boys that have reached sexual maturity and are now trying to establish their place in the social order between them. This means that we have an issue that is likely to continue with fighting as you have seen. In some male rat groups have no trouble if one is willing to be submissive. But when both lads are keen to be the dominant rat, we will see fights like this continue until one submits (or in the wild, one leaves). Since these rats are pets, there is no leaving option. This means that we run the risk of fights getting more serious and the rats being subjected to stress and potential harm.
In this case, I understand why you are reluctant to separate them. Still if one has an open wound, he needs to be separated from the other rat while he heals. If you are concerned about a full separation, consider dividing their cage with chicken wire (cover sharp edges) or putting two cages next to one another. This way the injured rat will have a safe place to recover but they will still be near enough to smell/see/interact and maintain a basic level of social interaction. For the injured rat, you may also want to consider using newspaper instead of bedding for him to maintain a better level of cleanliness while you are treating this wound. T
he other positive to having the cage set up like this just now is that you can have them both castrated (the only means of removing territorial behavior since we can't talk them out of this natural push for dominance). They can then both recover at the same time safely from one another but near enough to not become "strangers" (or territorial intruders). Once they have been neutered and 3-4 weeks has passed (the time frame for testosterone to leave circulation post neuter), then can be slowly reintroduced to sharing a cage/territory.
Overall, with two entire males scrabbling over domination, we are likely to see more fights in the future if they stay how they are. Therefore, before fighting becomes a habit and they fall out for good, it'd be worth considering neutering. And this may be the time to do so. As long as the wound isn't severe, his vet would probably castrate him at the same time they treat this wound. This would let them both recover from castration over the next few weeks (while the others wound heals) and you can get them back to living together with less drive to harm one another.
I hope this information is helpful.
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All the best,
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