Bandmate Marvin Humes revealed that Merrygold suffered concussion after landing on his head in the stunt.
Humes told The Mirror: "This show really has been blood, sweat and tears... and scratches. We're all injured. One of our dancers slipped a disc, one had a really bad neck injury and one a knee injury.
''Then Aston fell on his head which was pretty nasty."
Merrygold elaborated: ''It's been full-on. As well as landing on my head, I busted my knee and [JB Gill] did his, too.''
Humes further recalled how Merrygold "nearly drowned" during a water stunt, adding: "Our lives have definitely been at risk.''
Merrygold recently declared his intention to play pranks on his fellow boyband stars during the tour, which started only two days ago (March 14).
Watch the music video for upcoming JLS single 'Proud' below: