Allen is feeling a bit worse for wear after oxygen tubes that were stuck up her nose for the operation could have led to her nose bleeding for several hours.
She tweeted: 'I have had a nosebleed for 16 hours, I slept upright last night. Chapped lips, mouthful of blood. Not a great start to the weekend.'
But the 25-year-old has since been give medication to make her feel slightly better.
The Smile singer added: 'Oh, and hamster cheeks doesn't even cover it. I did get 10 mgs of morphine though, which was nice. *nods off*'