CycleOps Mag Trainer skewer doesn't fit
Many axle nuts for an internal gear hub will fit directly without modification. If yours does not, then there are options to fix that, similar to the set from Tacx below.

As with many issues with trainers, there is a solution available for this issue. 

This is a set of accessories designed to fit most solid or thru axle bikes.  You would need to make sure that you get a set that correctly fits your bike.

Details of the accessory kit here.