I actually agree with Wahine and CWB. You can have cracked or subluxed (and yes, even broken ribs) and not feel it right away. I xray pts all the time that didn't feel it until a day or two later. Sometimes it's obvious and sometimes it's hard to detect what's up. We do chest xrays along with the rib series to look at the soft tissue to make sure something isn't punctured or avulsed in the area. As for the cracks, we advise a followup set of xrays in two weeks if the original ones are inconclusive. If they were cracked, they will show a healing callous most of the time.

I'd advise some xrays just to make sure. Think of it as getting a bonus look at your heart, lungs, esophagus, mediastinum, etc in the process. I do hope everything is ok and it's just a bruising. Take care and good luck.