I grilled a boar boneless shoulder. It is dry. How can I repurpose this? Can I dice it & slow cook in BBQ sauce? Will this soften the meat a little?

Happens to the best of us. I would suggest slow cooking it at 225, covered in foil for an hour or so. I would pull it and mix it w/ either a high quality Carolina style BBQ sauce (which is thinner, spicier with more vinegar) or adding a thin concoction of your go to pork marinade. If you don't have one, think mustard, apple juice, and a T of some salt or soy sauce or worchester. A good vinegary slaw will also aid in offsetting the dryness. Good luck.

Have you thought about chopping it up or pulling it and making tacos? I find smothering anything in cheese, salsa, and avocado usually makes it delicious.

Do you have wild boar? If so, I am so jealous! Wild boar doesn't have a lot of fat, so it usually is braised or slow cooked in damp heat. I think at this point, I might cut the meat into tiny cubes--or grind it--and add it to a sauce (tomato comes to mind) for pasta. Italian recipes for wild boar abound--for future reference.