Pimples are a very mild skin infection and never leave scars.
Make it by mixing 1 tablespoon of bleach in 2 quarts of water. Open any pimples that have come to a head using a needle sterilized by alcohol or flame, and then throw the needle away. The pus should run out without squeezing. Wipe the pus away with a tissue. To prevent spread, ask your child not to touch the pimples or rub his skin.