Why is there a Small bulge under rib cage post tummy tuck? (Photos)

Thank you for sharing your question and photographs and I am sorry to hear of your bulge.  Without an in-person examination of the bulge it is difficult to render definite advice.  This may be the result of persistent muscle laxity, a discrete fluid collection, suture-related issue, or tissue swelling.  I would see your surgeon and voice your concerns, they can offer you the best advice. 

It is hard to say without having been involved in your surgery.It could be from the soft tissue elevation,  It could be swelling, it could be fluid.  Best to review with your surgeon.