First and foremost, congratulations that you have given up smoking. That's a first great step towards preserving your skin (and your general health). Secondly, the regular use at-home of prescription topicals, such as retinoids, alpha hydroxy acids, and niacinamide, along with regular and appropriate use of high SPF mineral sunscreens can go a long way to preserving your skin and promoting neocollagenesis and neoelastogenesis. A series of in-office, superficial peels consisting of high concentrations of glycolic or salicylic acid, Jessner's Solution or low concentrations of TCA can complement and supplement the at-home regimen. At only twenty-four and with only four years of smoking, the aforementioned approaches should go a long way to help to preserve and rejuvenate your skin. Finally, at least from the one photo provided, there appears to be some volume deficit in the cheeks, which not only is contributing to a diminution in the Ogee Curve, but giving rise to incipient tear troughs. If this is indeed so, then the use of a robust HA volumizing filler, properly injected can address these issues. The results of this treatment are typically immediate and treatment typically engenders little to no significant downtime. You would be wise to consult with an experienced, board certified cosmetic dermatologist who can help you with all the above treatments. Best of luck.