M small dog ate a rib bone whole. Will he be okay?

If he throws up, that may be an indication of blockage, you would need to get to a vet ASAP. Keep an eye on him, I wouldn't leave him alone.

I just noticed you said a small dog. The smaller the dog the bigger problem it can be. I would call your vet's office and ask to speak to the vet. Discuss it with them to see if a visit is warranted immediately.