Have Cat Questions? Ask a Cat Vet Online.
If it is a broken rib, the main thing is to make sure your cat is breathing okay (didn't puncture a lung). There isn't anything safe to give over the counter for pain medication, though. You will need to keep your cat indoors and confined to a pet carrier or small area for 7-10 days while the rib is healing. You could try to call your vet and see if you can get something for pain while it is healing.