What Causes Red And Dark Spots On Face After Derma-roller Treatment?

hi...myself maya i have done derma roller treatment on my cheeks becoj of scars....but still it has some redness and dark spots on my face what is the best solution to get rid of this?? Also at my mouth corner are getting black..i asked doctor he said that it is allergy of salima...is there is any cream or gel for this??/