My son had a small skin infection from a pimple on his face been taken care with bacitracin and its cured, but he still has a dark spot whatcan I do?

Sunscreen, exfoliate. The dark spot is a hyperpigmentation scar that will fade on its own. The most important thing is to wear sunscreen everyday as the spots can get darker in the sun. An over-the-counter cream containing retinol or aha can help exfoliate the spot and speed the healing, however these creams can irritate the skin. Even with the creams it will take a few weeks to months to heal, so be patient.
Hyperpigmentation. Postinflammatory hyperpigmentation (pih) is a frequently encountered problem and represents the sequelae of various cutaneous disorders as well as therapeutic interventions. This acquired excess of pigment can be attributed to various preceding disease processes that affect the skin such as infections. Bleaching cream like hydroquinone is effective.
Dark spots. Post inflammatory pigmentation as it is called can be treated with bleaching creams, laser and may fade over time.