Retinol increases cell turnover, which can help fade your acne scars faster. Get a prescription cream from your dermatologist or buy a weaker, over-the-counter retinol. It may take a few weeks to see effects. Creams won't really decrease your scarring, but you can use over-the-counter creams to bleach skin that has been darkened by scars, minimizing their appearance. Be sure to use sunscreen of SPF 30 or higher on your scarred area, as well, because scarred and unscarred skin tend to tan differently – scars are less noticeable when they blend in with the color of your surrounding skin. Some people find that rubbing vitamin E oil on their scars reduces their color and appearance. You can try this method by applying vitamin E oil to your scarred area, leaving it for 15-20 minutes, and washing it off with water. Do this regularly and watch for improvement. Wash your chest and pat the area dry. Use a cotton ball to rub fresh lemon juice onto your scarred area. Leave this on for about 10 minutes, then wash it off. This hasn't been scientifically proven to decrease scarring, but doing this weekly may lighten the appearance of scars over time. Lemon juice can make your skin more sensitive, so always wear sunscreen on exposed areas when you're outside. If you have mildly raised scars, you may benefit from using exfoliants made from natural ingredients – similar to a very mild at-home dermabrasion. Try periodically using one of the following natural remedies to see if scars appear smoother or lighter over time:  Mix honey and a little milk to get a paste. Apply this to your scars and leave on for a few minutes before rubbing it off with a soft, clean washcloth in the shower. Mix 1 tablespoon of baking soda with 2 tablespoons of water. Rub this onto your scars in a circular motion and leave it for 2 minutes. Wash it off with fresh, warm water. Preventing acne scars is easier than treating acne scars. See your dermatologist for medications as soon as you start to experience chest acne. You can also try to reduce your chest acne with natural remedies, such as:  Do NOT pop your pimples. This can cause infection and worse scarring. Get about 15 minutes of sunlight on your acne-prone areas each day – not enough to get a sunburn, though. Drink 7-9 cups of water a day to stay hydrated and help your body flush out toxins. Wear clean clothing, and change clothing often to help decrease the risk of chest acne.

Summary:
Apply retinol over your chest. Use bleaching creams and sunscreen to minimize color contrast. Try vitamin E oil. Use a lemon juice application. Try a natural exfoliant for mild, raised scars. Prevent chest acne.