It's correct that chicks are tougher than they may appear, and heal quickly. But you're right to be concerned about infection.
I had a two-week old chick last summer that got pecked so badly by my rooster, she was literally scalped. She had a gaping wound, and from your description of your injured chick, far worse than yours. But it never got infected, and she healed completely, re-growing new skin and feathers.
The big secret is to cleanse the wound twice daily, morning and right before bedtime. Use peroxide or soap and water.
The second part to the secret is to keep the wound MOIST! Be very diligent about this! Do not let the wound dry out! This will prevent premature healing that can conceal infection underneath.
Blu-kote, while a useful disinfectant, won't keep a serious wound moist. Neosporin will work, but what I used was Silvadene. I had some left from when I had been badly burned, and I figured if it grew me new skin, maybe it would work for my chick. It did. And the silver in it prevented infection while keeping the wound moist.
Ay one point, I thought the chick was healed as well as she was going to, the wound being almost closed, but not quite. I quit treating it. It didn't get infected, but it stopped healing. I resumed treatment, going back to being faithful about keeping it moist, and healing resumed at a pace that amazed me.
It probably won't take as long as it did for my chick to heal, so I think your chick has an excellent chance to be good as new in no time if you commit to serious wound care.