Hypertrophic Scar from Abscess on Chin?

Hypertrophic scars from acne and pustules can be improved with pulsed dye laser and topical creams. I would recommend Melarase cream for the dark spots and discoloration.

From the description it is hard to know whether the residual lump is from residual, smoldering inflammation, scar tissue formation or the re-formation of a small sebaceous cyst. If either inflammation or scar tissue, the injection of a small amount of an antiinflammatory agent, such as triamcinolone acetonide suspension may be helpful. If a small sebaceous cyst is at the root cause, then minimal incision drainage would be helpful and would pose little threat of visible scarring--critical when treating anything on the face. 

Small incision drainage consists of making a small nick in the skin (under 3mm) with a very fine #11 blade scalpel and then inserting a very fine curet (a scooping instruments) and sweeping out all the cyst sac contents, being careful to ensure that the capsule (the wall of the cyst) is removed as well to prevent future recurrences. Only a drop of local anesthesia is needed to anesthetize the intended nick site .

Performed in this fashion, no suture is typically required and the wound with a virtually scar or often none at all. Results are typically quite gratifying.

Unless the entire cyst cavity was removed this cyst will come back. Please seek some professinal help from a plastic surgeon for excision