Acne and dark spots are common at young age. Do not pinch, pop or squeeze any pimple as it an cause scarring and pigmentation. Do not apply any home remedies
which can aggravate the situation. You can apply clindamycin
1% gel and doxycyclin capsule by mouth for 15 days of period. The other of the creams such as Azelaic acid, glycolic acid
and kojic acid
can be used to reduce the pigmentation.
You can also go for latest treatment including chemical peeling and lasers to get early relief form the problem.