Moth balls are a biohazard all around, and best not used for anything, not even moths.

We had a skunk living in the green electric company box in the utility easment in our back yard (it was where the electric service wiring originated for several houses in our part of the block). I called the power company and he got rid of it very easily. He sprayed the box with an industrial equivalent of WD-40, used a whole can. Said they'd figured out that skunks didn't like the smell of it and would go away and stay away. It worked.

I'd board up the hole after you get your uninvited guest out of there. Rabies is a big problem in skunks in North America. In Texas they have resorted to studding chunks of meat with doses of rabies vaccine and throwing them out of airplanes for coyotes and skunks and other meat eaters, to try to keep the rabies down.

SRS