My 60-lb dog ate a nectarine pit?

I left him in the care of my mother while I went to work, I should have known better... He ended up snatching a nectarine pit off the counter while my dad was carving one up and my parents did exactly nothing about it. They failed to even inform me until several hours later. I know they have poisonous cores and I'm not sure if my dog is big enough to pass it successfully. Is it too late to induce vomiting?