He clearly knew he was injured. He went to ref to show the impact of Carra's tackle. Even i was able to walk that much distance with Fractured leg. Fabregas played with Broken foot at Emirates against Barca last season.
Injured doesn't mean he can walk anymore. It was there for everyone to see the anguish on his face He was in tears. And sadly people were making fun of that..
What do you expect when a player with a reputation for diving like Nani does something like that? Running to the ref makes people assume it was a dive, and it was made worse when he went down when Gerrard touched his shoulder.
Seriously, even if he is injured, it's common sense that you shouldn't act like that.