A dent should be enough to let the air flow in. As long as it can breathe and move you have nothing to worry about. If you're so concerned you can peel off the shell at the dent, but be conservative and only make realllllllly small hole.
If an active egg stopped moving I'd be worried. Are you able to candle it right now?
One of my previous eggs got to the internal pip but a day after it was dead. When I took a look I found some gooey substance blocking its nostrils, it died from suffocation. Probably it only internally pipped half-way and got suffocated by the albumen.
If your said egg already peeped before then it completed the internal pip, so won't die like that one of mine, but it can still run out of air, which is why I always make a safety hole. Not everyone does, but I do.
In any case keep talking to them. If they're alive they'll be encouraged to come out by that.