Ariana Grande burned her "butt cheek" shortly before filming a key scene in 'Wicked'.The pop star - who is nominated for a Best Supporting Actress Oscar for her performance as Glinda in movie-musical 'Wicked' - has confessed she injured herself during her lunch break and needed to have ice packs applied to her behind while she was shooting the 'Defying Gravity' sequence with co-star Cynthia Erivo, who was also thrown off after her meal included her most-hated vegetable.Speaking during a Q A with Variety at the Directors Guild of America , Ariana explained: "Long story short, we were filming 'Defying Gravity'. "And two things happened right before that shot. We had broken for lunch and for some reason that lunch had so many onions in it and Cynthia was like having a heart attack and also the steamer had burnt my butt cheek.