Hello, it's normal for skin to undergo few changes as you approach adulthood. A regular skin care routine consisting of a face wash preferably containing ingredients like Salicylic Acid and/or Glycolic acid followed by a gentle non comedogenic sunscreen in the day and a night care cream containing Azelaic acid will help. Additionally you can follow a simple balanced diet avoiding excess oil, junk and processed foods. Include a lot of fresh fruits and vegetables in your diet. A vitamin C and omega 3 fatty acid supplement may help too. But do remember, do not try any thing without a proper examination and prescription by a doctor.