There is a great variation in post-operative recommendations following SmartLipo depending on your surgeon. In my experience, patients who have SmartLipo of the neck do very well with the following protocol: compression garment and limited exercise for 48 hours, followed by normal activity for...
Skin discoloration can result from unfinished wound healing, residual blood, scarring, and melanin or iron deposits at the site of cannula insertion. These defects can be treated with certain lasers, microdermabrasion, and sometimes with surgery.
Its possible you have some lingering swelling or inflammation that would go away with more time. I would wait at least 6 months, but if it doesn't go away you probably have some underlying gynecomastia that is more sensitive because the fat was removed around it but the hard glandular tissue ...