The leader took a short fall on the second bolt and swung into the side of the corner they were trying to gain. They still had their belay device (GriGri) racked on a back gear loop on their harness. This punched into their back, leaving them very sore and tipping them into an inversion. An imprint of the device was visible on their back afterwards. A minor injury, but it could have been much worse if it had impacted against the spine or organs. Casualty walked off in discomfort.