She "cut the ball of her foot, quite severely, on glass two days ago," Beau Nelson told People.com, adding she was in "a little bit of pain" as she posed for photos and answered questions before the prize presentation.
Stewart didn't take her crutches on stage when she presented an award with actor Daniel Radcliffe later in the evening.
People.com did not report any other details about how Stewart sustained the injury.
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'
Beyonce flaunts bikini body, Blue Ivy in vacation pics