Hematoma or hyperpigmentation after lower blepharoplasty? (Photo)

Given the photo and your story, this likely represents hyperpigmentation as a reaction to the surgery and subsequent inflammation. This usually resolves on its own, but it's important to take measures to prevent it from worsening. I recommend dark sunglasses and at this point in the healing you can also use sun block to prevent further sun exposure. If it is worsening, bring the issue up to your doctor, as topical medications and treatments such as hydroquinone can be very helpful.