"I admit that I get a little queasy, especially when it comes to blood around my arms," Franco told PEOPLE at the Palm Springs International Film Festival opening night gala. "When I go to the doctor for a checkup and they draw blood, I admit, I'm not good at that at all."
However, "when I watched that scene, I was fine," Franco, 32, says with a laugh.
Although Franco's onscreen pain was purely fictional, the actor was anguished in other ways while shooting scenes for the movie.
"A lot of the physicality was real," the 2011 Academy Awards host says. "I was really being bruised, and the frustration and the emotion would arise in an organic way as well."