Bump under belly button after TT? (Photo)

The fact that it only appears when you are flexing would indicate that it has to do with the new position of the muscles.  It does not sound like something that you need to be worried about I would visit with your plastic surgeon to get examined and person as that is the only way to tell for sure. Best of luck!
Dr. SubbioBoard-Certified Plastic SurgeonNewtown Square/Philadelphia, PA

To give you a good answer you would need a hands on evaluation. Best to check in with your PS.Best wishes.

Thanks so much for reaching out.  It's hard to say exactly what this can be without an exam but it could be a seroma as you described however I don't think so. More likely the muscle repair is a little bunched up beneath the belly button and when you go to sit up it bunches up a little more. There's also a chance that it can be a hernia. I would be sure to see your plastic surgeon to get an exam in properly about you waited.  I hope this helps :-)