Hi, I can understand your concern for scars and marks after cystic acne. These marks are activity of melanocytes in the superficial epidermal layer of skin or due to atrophy of the skin leading to scarring. Lightening agents such as Kojic acid or azelaic acid cream application which you can use under dermatological guidance. Alternatively tretinoin can be used in combination with lightening agents to reduce the scarring. There is an option of chemical peels and laser treatment according to grade of scarring which can be used. Eat healthy diet containing lot of Vitamin A and Vitamin C. The most important part in treatment is by sun protection by all measures. Take a proper guidance and follow up with a good dermatologist so that all the problem of pigmentation can be dealt best for future time. Take care