I've had 3 pip at the wrong end in the past, 2 made it out on there own, one I had to help. If it's still not out 36 hours after the external pip, go ahead and help. If you don't know how, here are the basic steps.
Carefully take something small, you can use a paper clip streched out, or I usually use an extra pen from those nintendo ds things. Break off small bits of shell going around in a circle slowly breaking the membrane as you go as if you were zipping for him. If you see any blood, stop and put him back in, he's not ready. But if blood never appears, then more than likely he is ready to hatch. Once you get all the way around the egg, put the egg back in and let him push the two halves apart himself. If he hasn't pushed the two halves apart in 3 hours, then go ahead and gently take the top halve off for him, if their is no yolk remaining, you can take the bottom half off and lie him down gently. If there is yolk, then leave the bottom half of the shell on for a bit later. Some people like to do this process in a bathroom in which the shower has been running with hot water so that the room is hot and humor similar to incubator conditions, but if you don't have the egg out too long, than don't worry about it.