They can take a couple of days. I’ve only lost one chick due to it being too sticky in the egg and couldn’t manage to get through the shell. The other 20 just took some time. Yours could still be absorbing yolk.After you hear an egg whistle, approximately how much time does it take to start hatching? The egg has been wiggling and whistling when I talk to it for the past 24 hours or so, but hasn’t externally pipped yet.
I would caution against assisting. They can bleed out pretty bad if a vein is hit or severed in the assisting. If you feel confident enough, you can try making an air hole if it’s taking longer than it should. But that’s risky as well.