What makes you think it's too dry? Take the average relative humidity of your area and that should get you pretty close. As said above, unless you live in the desert you may need to be thinking in the other direction. Hickory can perform at lower moisture level as compaired to other woods. I like it around 6.5%, I would be nervous below that, but I believe it can go higher, maybe to 10% and still be OK to work with without being too wet. Google the average RH of your area and see where you land, wood will be at equilibrium with its surroundings with whatever it is or very close.
Just hard for me to imagine the need to add moisture back to Hickory.
As Jawge said, the quality of grain could be the bigger concern.
Greg