I'm with Marc. This is exactly how twisted grain splits when you try too hard to twist it straight, and apple usually twists. Just happened to me on a BL stave with rollercoaster wobbles and some snakes. I was trying to coax the limbs into approximately the same plane at the fadeouts, but the thicker handle section split a lot like that, and lifted in two kitty corner spots on the belly side.
I'd glue it down with the strongest glue you have access to, and keep going cautiously. If the split was close to the grip, you may consider gluing down the splinter, flattening belly side, and adding another little slat to stiffen the handle a bit.