What can I do to minimze the appearance of my 16 year old scar? (photos)

I'm really sorry that this has happened to you. It's frustrating to me, however, since I continually caution people to exercise a healthy dose of "buyer beware" when considering treatments with "bells and whistles" lasers and other so-called energy-based gizmos. At least from the photo provided, the "chunk of collagen" is likely to be a hypertrophic scar that developed in response to the CO2 laser treatment. Fortunately, the use of intralesional injections of an anti-inflammatory agent, triamcinolone has an excellent many decades' long track record for successfully shrinking and flattening hypertrophic scars from all causes. You would be wise to consult with a board certified cosmetic dermatologist. and best of luck.

In my opinion, you developed a hypertrophic scar after the CO2 laser procedure. It should respond to a combination of 5FU and steroid done intralesionally or a topically after microneedling. Cryotherapy with Liquid Nitrogen should also be helpful. Find a scar expert.
Jeff Rapaport MD FAAD
Realself Hall of Fame