OUCH! That looks nasty!
I assume you are not going to take your kitty (or any animal,) back to that groomer?
The groomer should have notified you of this when you came to pick kitty up. That's not very professional.
And I would say yes, if the kitty requires vet care/possible stitches or i=antibiotics -then that groomer should, at the very least, HELP pay for your expenses but don't count on it.
(Did the groomer ever have you sign any paper work? If so, I'd read it to make sure the groomer doesn't have a hold harmless clause that you agreed to.)
As far as how bad it really is, I'm no vet but have had at least 30 cats in my life time, maybe a few more. I have 5 right now. As long as you keep a good watch on that -make sure there's no oozing of puss, and especially watch for the area around the gash to swell & get red. If that happens -I'd take kitty to the vet (worry about trying to get the groomer to pay afterwards -BUT either way; I'd at the very least notify that groomer of this so the groomer can't say that it happened AFTER you brought your cat home.)
It does look "yucky" but I've seen much worse and the cats heal pretty good on their own. I have used hydrogen peroxide on my cats with no harm done (to make sure the wound is clean.)
Just soak a cotton ball in it and gently dab or even squeeze it out onto the wound a couple of times to flush off any bacteria.
I would not put anything else on it (like salves ointments,) because you know the cat is going to just lick it off & it might possibly make the cat sick.
Just keep a good watch on the wound and everything should be just fine.
(If swelling & redness or puss starts coming out of the wound; if it were my cat; I'd take her to the vet.)
