I would leave it be, I have had eggs like that in the past, once in a while it will require help but sometimes they can hatch on their own. If it manages to make an external pip, wait until after 24 hours to help. If you notice that it has pipped internally, you can help by make an external pip for it 24 hours after if it still hasn't figured it out on it's own. If every other egg has either hatched or is a dud, go in and make an external and internal pip, but at that point there won't be must hope.
So in other words leave it, and see how it does. If it's expensive then watch for the internal pip, but my advice to leave it and pray it pips externally, if it's still not out in 24 hours after the external pip, help it. Sometimes they do hatch on their own.