I had one in my last batch pip at the wrong end. I did assist, when it became apparent the chick wasn't able to make much of any progress. It hadn't ruptured the air pocket, and as a result didn't have room to maneuver. Whether you assist or not is a decision you'll need to make, but if you do, proceed with caution. Just take a little bit of shell off at a time, checking the membrane beneath to ensure it doesn't have any blood vessels in it. At four hours, the chick may still be absorbing its yolk - normally they pip into the air pocket, then spend some time at that point before they pip externally, rest again, and finally work on getting out. This chick will have had to pip directly to the outside, without that break between the first breaths and trying to break through a tough shell.
If it were me, I would open up the pipped spot enough to ensure that the chick can breathe, then give it several more hours to see if it can finish up on its own before doing anything else.