Illness/Sickness: My Axolotl has broken it's arm?

My golden axolotl seems to have broke it's arm 3 days ago, it twists up abnormally and the hand of it is swollen and red. It's actual arm above it's hand is white (Not like the bacteria, almost as if the blood circulation isn't there). I think it either got caught in a filter or was attacked by it's partner (I've had them both in the same tank for four years, never really had any big concerns about that either). He is still eating and moving around fine but I am a bit of a novice when it comes to these. He looks as chilled as his usual self and doesn't seem to have any discomfort, and is eating better than he usually does during the winter period. Is there anything I can do or should I just let nature take its course with him? I am fine with it growing back abnormally so long as he is okay, and he can still seem to swim about pretty well. Although I am more concerned about how the hand is swollen and red.
What could I do?

I would just make sure the water is kept very very clean and cool.

Keep an eye on it for fungus. If you see the cotton wooly growths of fungus you will need to give him a salt bath.

I suspect his tank mate did it by accident at some point.

Hope he recovers well.

It could be worth posting a picture as it might be worse than i'm imagining.

Mel