Hi Red Rider!
Sorry to hear about your injury... a least it didn't happen during a rest break in the middle of a long ride
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It's fairly common, given the mechanism of injury, to disrupt the function of the costovertebral joint--the joint formed where the rib articulates with the vertebra (yup, it's a real joint just like the bigger joints, with articular cartilage, a joint capsule, and all that).
With a force such as you sustained to the rib, the head of the rib can be driven forward and most likely even rotated (when you inhale/exhale, your ribs not only lift and rise, but "spin" or rotate at the vertebrae).
A quick test (suggestive, though not necessarily diagnostic) is to push with your finger tips along the side of your sternum ("breast bone") on the same side as your back pain. Press fairly hard. If you find a spot on or between the ribs that is very painful and perhaps even hurts in your back, then you've likely a subluxed rib.
If you fractured the rib, it'll get better in a few weeks. If you've "subluxed" the rib, it may or may not resolve itself. If the pain persists, see a good Physical Therapist.
Good Luck!