16 days post tummy tuck, could this be a hematoma/internal bruising? (Photos)

Thank you for sharing your question and photograph.  It appears that you have developed a hematoma which can be treated with either aspiration in your surgeons office, typically after 2 weeks, or can be allowed to resolve on its own, if small.  Follow up with your surgeon closely to ensure no further healing issues develop, and resolution of your hematoma occurs.  Hope this helps.

From your description it sounds like it could possibly be a small hematoma.  They will typically dissolve on their own.  Continue to follow the advice of your plastic surgeon and communicate any changes or concerns.