I understand you feel horrible about this, but didn't do it on purpose. It's great you wanna take care of the juvenile garter.
Although the wound does look very nasty, I think he has a good change surviving it. I once had a garter with a bad wound from badly bitten by an other garter and I thought he wouldn't survive. But after cleaning it and put him in a clean tank, it actually did heal after a few weeks
I think it's important to save him from a lot of stress, so the towel is a very good idea! And to keep the wound as dry as possible, ofcourse it's good to clean it, but keep it dry after that.
It's suprising how garters can heal from a bad injury. Of course this is no quarantee, but only speaking from our own experience.
Good luck with the young garter.
And btw, welcome to this forum
