There's lots of different kinds of Nyla's out there but i'm assuming you gave him one of those edible varieties? Looking at the ingredient list of their website, your bully may have sensitivities to any of the following if they're not used to it:
Wheat starch, glycerin, Powdered Cellulose, lecithin, potato starch, chicken powder, roast beef flavor, natural bacon flavor, natural flavor, oat fiber, calcium carbonate, soy flour and rosemary oil. Vitamins: Thiamin, Riboflavin, Pantothenic Acid, Vitamin B-6, Folic Acid, Vitamin A, Vitamin E, Biotin, Choline, Inositol and PABA. Minerals: Calcium Carbonate, Ferrous Carbonate, Magnesium Oxide, Dicalcium Phosphate, Potassium Chloride, Sodium Selenite, Calcium Chloride, Zinc Oxide, Copper Oxide, Manganese Oxide and Sodium Molybdate.
I've given mine the edible Nyla's before w/out any adverse effects but you may want to stick to the non-edible Nylabones instead for Jackson. Or deer antlers are also a great alternative.