Kerry Katona is planning to go under the knife for an operation to fix her “saggy” chin. The 43-year-old former Atomic Kitten star recently underwent reconstructive surgery on her nose to fix damage from years of drug abuse, and she’s already looking to the future and planning another operation to tighten up the lower part of her face. In her column for OK! magazine, she wrote: “I’ve been under the knife a few times myself for the odd nip and tuck, and I think the next thing on my list will be my chin. “I’m at an age where the skin is beginning to sag and I’d like to get it done to make myself…