Yes, he does need immediate attention. If nothing else, he needs stitches and antibiotics. If he doesn't see a vet right away, the cut will get worse and get dirty (fur, cat litter, floor dust, etc). He'll lick at it, which is natural but will keep it from healing cleanly.
Lastly, it will very likely get infected from the dirt and stuff which will cause a worse problem and a more expensive vet visit.
Keep us posted as to how he's doing, ok?
Hi,
I'm sorry your cat is hurt, but I'm not sure what you are looking for from us. This sounds like an emergency which means taking kitty to the vet immediatly.