Those scars are called P.I.E. They form after your acne bump is going away. Those scars take quite some time to go away. Of course there are some things that you can do. You can try a vitamin C serum to help speed up the process. Or try a derma-roller. Which has little needles and that helps the skin to re-growa new layer. And if you are really impatient you can look into getting a laser done. Its pretty expensive and you would probably need more than one round. I hope i was of some help to you.