Hi ..dear user -
welcome to HCM..
Marks after pimples are called 'Blemishes' in medical term..,
this is called Post Pigmented Inflammation...
it has very good treatment...
1) Frequent washes of face by Triclosan and zinc oxide
2) Topical treatment is..morning times Sunscreen lotion ( Suncote ,Sunkare,or Melaguard ) evening times....lightening creams i.e.Kojic acid
with vit C or Combination of Hydroquinone
and Momentasome gives very good results..i.e 70%
3) Inexpensive procedure...RF-Demelanizing technique...Using RF (RadioFrequency) remove all black marks after using Lightning creams ..70to 80% results
4) Expensive treatment like LASER treatment
...here giving 1064 nm of Q Switched nd:YAG Laser and Ideal Laser is Long and continuing mode with heavy and bulky Laser system i.e. Q Switched Ruby -carbon dioxide combination will delivers a flat topped beam utmost perfection ... now days commonly used Laser....
hence choose the treatment.., do accordingly... ok... goodluck