Update: The Answer appears to be that he was bleeding originally. But then there is an absence of blood between his release and CBC interview, when the blood returns.
And yes I did edit some of this post without adding strike throughs, because I don't like strike throughs.
CBC notes that protester Jeh Carter acquired a bloody nose sometime after leaving Parliament Hill and before being interviewed by CBC.
PS. he's definitely not bleeding here.
Akins tells it differently here. But this (note: Jeh Custer=Jeh Carter):
One of those arrested, Jeh Custer of Edmonton, was seen bleeding from the mouth after his head struck the concrete walls inside the House of Commons. Custer was observed with his hands handcuffed behind his back, being escorted by two uniformed RCMP officers into the basement in Parliament Hill's Centre Block.
Doesn't seem likely likely unless Jeh cleaned up his mouth and added blood later.
Update: David Akin says our guy was indeed bleeding inside the HOC. But then there is still a period in which Carter/Custer is bloodless, and then shows up bloody again at the CBC interview.
Update Again: All of which doesn't explain where his injuries came from in the first place.
Even More Update: CBC's Janyce McGregor mucked up her times in original article. First shot (bloodless) is from about 4:38pm (not 2:38), CTV's bloodied shot from 5:17. Pretty clear the blood is coming from over the nose in 2nd shot.