Kizaru thought to himself that the attack wasn't good for him, so it definitely wasn't him faking it at first. The real shocker is the lack of blood, I think the lack of bleeding is just Oda trying to maintain Kizaru's aura. Kaidou bled from a much much much weaker version of the same attack.
Oda knew he was gonna sideline Kizaru, he wanted to make it obvious that Luffy was not the cause, hence he made him look squeaky clean and even had the fodders ask him where his invisible wounds are, to which Kizaru implied it was mental.
Oda knew he was gonna sideline Kizaru, he wanted to make it obvious that Luffy was not the cause, hence he made him look squeaky clean and even had the fodders ask him where his invisible wounds are, to which Kizaru implied it was mental.
