It would be best to play it safe and see the vet. When working for the vet, we instructed owners of cats who ate chicken bones to monitor for signs such as vomiting, lethargy, not eating, straining, diarrhea or abdominal pain and to consult us without delay if any such symptoms appeared.
Your cat is manifesting two of these symptoms, which make a blockage more likely although the fact you heard your cat crunching the bones up is rather reassuring.
On the other hand, cats may too get diarrhea and lack of appetite simply as a result of eating something they are not used to. So it's difficult to say what is going on. When in doubt, it's always best to err on the side of caution and see the vet to play it safe.