"It was a difficult moment for me, because you have the crowd chanting 'One more match' and I wanted that one more match. It is time, for several different reasons, but it was hard to do after 30 years," Sting said.
The former WCW, NWA and TNA Champion explained his injury, saying that he wasn't able to control his legs after one of the spots in the match.
"At Night of Champions against Seth Rollins, there was like a whiplash that happened twice in the match. The first one was shock and numbness down the fingers, and I've had that before, but this was pretty severe. The second time it happened I lost control of my legs. Long story short, I have spinal cervical stenosis in two areas of my neck," Sting said.
Doctors told Sting he was lucky that he walked out of the ring. You can see the full interview at this link, where Sting explains his WrestleMania moment, and talks about how happy he was to finally appear for the WWE.