The 26-year-old 'The OC' star, who is playing James Gordon in a pre-Batman Gotham City, posted Instagram pictures of the wound he sustained on Friday.
He explained that the injury happened as a result of filming a fight sequence, before adding, "Don't ram your head into concrete pillars, kids."
McKenzie noted that the incident also took place on his 36th birthday.
The wound was successfully stitched up, and the actor is expected to be back on set.
'Gotham' focuses on the earlier years of James Gordon on the police force, as he tries to stem the sea of corruption that is destroying his once-prosperous city.
It was recently announced that Netflix had gained streaming rights for 'Gotham' ahead of its series premiere.
'Gotham' debuts on Fox in the US on September 22. Channel 5 will air the show in the UK.