There is no nut on the end, just a tiny little hole in the center of it.
I should've thought of this earlier and asked my dad to pick up the tool when he got the filter cartridge (which also included the rubber o-ring) But the problem was, when he last had his oil changed, it was at a fast lube place, and they told him his car used a regular oil filter. I wouldn't be surprised if they never changed it at all and he's still running the OEM filter cartridge! (which really has me worried since he'll be running this OEM cartridge right up until he hits 12,000km)
Hopefully it's not too expensive at the Volvo dealer, as that's probably where he'll pick up the tool.
One other thing with this car that is a bit of a pain is the removal of the skid plate underneath it. That eats up about 3-4min at the beginning and end of each oil change.