For blackheads and pigmentation treatment (specifically dull skin), following methods can prove to be effective:

1. Over-the-counter treatments: buy medicated creams/gels which contain the following as their ingredients - salicylic acid, benzoyl peroxide, and resorcinol. They eliminate bacteria, remove excess oil, and clear your skin off of dead skin cells. These acids can make your skin sensitive to sun however, so include sunscreen in your daily skin care regime!
2. Prescription medicines: which will either contain stronger version of above mentioned acids, or will include more as well!
3. Comedone extraction: wherein the doctor will use some device to extract the pug causing blackhead.
4. Advanced clinical therapies: such as laser, microdermabrasion and chemical peel.

These treatments can be performed by a clinical doctor of relevant field only, which in this case would be a dermatologist, you can use our page to find them - Dermatologists in India.