Garter Snake Nicked by Lawnmower - First Aid?

[Tenevanica]

I was out mowing my lawn, and it appears I may have accidentally ran over a garter snake. (It may be Thamnophis radix but I'm not sure.) I hate hurting animals, so I was wondering if anyone here could help me with some first aid for the said snake.

The snake was just nicked about 3/4 of the way down its body. The cut is small, though it appears deep. The snake is unresponsive to most stimuli, though is definitely still alive.

I don't keep snakes, but I figured someone here could help me out with some first aid information. Maybe I can save its life! I appreciate any advice!

(I was going to get a picture of the wound, though it appears to have closed itself up, (?) and I cannot locate it. The snake is still unresponsive to touch, and is only slightly moving its jaw and curling its tail.)