Candle and if all is well, if it's FINE, then use cling wrap, saran wrap or press n seal, to cover the hole you made.
Normal hatching the chick actually REQUIRES the air restriction of the shell to generate the spasms and reactions that are "hatching". So a peek and a normal chick mean you need to close it back up, some people have used tape.
A peek in the hole and candling that show a problem means you need to get started helping them out, small bits at a time and I always close most, 90%, of the opening I make with press n seal, to keep it humid in there once I'm done with each step of helping.
First steps are find the beak and make a tiny tear to get the stuck little thing some more air. Often just access to more air after being stuck gets some going.
Once you know where the beak is you can CAREFULLY with a damp NOT SOAKED q tip wet some of the membrane you can see. Be super careful about not getting water in the chick's beak - if you can't see the beak never introduce water or damp into the egg.
After that put the chick back to warm, rest and decide if that's enough help. Often it is.
If not every couple/few hours help a little more. Patience. Once they can breathe there is no hurry. Just chip away in a normal zip pattern and nudge any membrane that doesn't bleed back with q tips or tweezers, damp it again, let the chick rest.
Usually the stronger ones hatch themselves within the first few steps of the process. Weaker ones you may need to take all the way. Just go slow.