If your temperature has been running a little low then that can cause them to hatch late. Candle it if you can to see whether it has internally pipped, or hold it up to your ear and see if you can hear a tapping/clicking sound. It's not the chick tapping on the shell, it's actually it starting to breathe for itself.
I wouldn't intervene unless the chick becomes less active. That would indicate it is running out of oxygen if it has internally pipped. Chicks pip internally then around 24 hours later (on average) they pip externally. Then they will sit and absorb the remains of their yolk and the blood that's been running through the veins of the membrane before unzipping and hatching completely. That phase can take 24 hours, sometimes up to 36 hours to complete. The unzipping only takes up to an hour of that time, and the absorbing stage is a very crucial stage, so it's best not to intervene if at all possible, because of the risks of jumping in too soon and doing more harm than good.
In the articles section there are great articles on the subject of assisted hatching so have a read through those before doing anything.
Your chick may also be slow because it has no other chicks to talk to and bond with which encourages them to hatch. If at all possible find it some friends as otherwise you will have a very needy, lonely, noisy chick on your hands that will need a lot of attention. A soft toy to cuddle with or a little cloth to snuggle under in the brooder can help as can a mirror, but it is programmed to bond with its parents and hatch mates and you will have to be those for it if you can't find it some friends.
