He had an early 1.3-second lead whittled down to less than 0.2 seconds with 1000m remaining but powered home to win by nearly two seconds.
"Everyone says bronze is my colour," he said. "It's my first individual medal at a worlds in 11 years.
"It's a big achievement to medal at the worlds and I've done it with the boys all the time in the team pursuit. It's grouse to get my own.
"Not every cyclist or athlete gets to do it let alone compete at this level for so long. To have all the medals to go with it is awesome. Although we only got bronze in the team pursuit, some big gains can be made and the young guys [in the team] are only going to get stronger."
Ryan's medal was the high point of an otherwise frustrating day for the Kiwi riders.
Olympic bronze medallist Simon van Velthooven was one of the favourites in the keirin, and won his first-round ride, but was disqualified early in the second round when he overlapped the derny (motorised bike) which paces the riders until the last 600m.
Eddie Dawkins, who rode the anchor leg in yesterday's gold medal-winning ride in the team sprint, struggled with a mild groin strain and failed to progress to the second round in the keirin, Dylan Kennett was seventh in the men's 15km scratch race and Shane Archbold eighth in the individual pursuit.
Dawkins is expected to be fit to make the startline for today's (NZT) individual sprint and New Zealand will hope to pick up more medals today when van Velthooven goes in the kilo time trial, Tom Scully rides in the points race and Aaron Gate begins his defence of his world omnium title he won in Belarus last year.
Gate was a surprise winner last year, not the least because it was his first omnium start at international level and second or third overall (he can't remember). The omnium is made up of six events competed over two days.
"Last year was my first international omnium so I won't be able to sneak under the radar like I did last year," Gate said.
"I think it's natural everyone will have an eye on the defending world champion. Hopefully that's something I can thrive on."
Gate has his eyes on competing in the omnium at the 2016 Rio Olympics and is also targeting a medal in the team pursuit after collecting bronze on Friday.