Pimples may leave post-inflammatory hyperpigmentation as black spots. Use good quality broad spectrum, non-comedogenic ,gel based sunscreen thrice a day on all over face.it will help by reducing black spots. You may need topical depigmenting cream as well as chemical peels if required
Next Steps
show to nearby qualified dermatologist for further treatment
Health Tips
don't pick or rub the pimples, use sunscreen daily.