The muscle tightening sutures run from the sternum to the pubic bone, skipping over the belly button. The muscle repair sutures may have ended above the indented area, allowing the muscle to spread in that area. The problem can likely be corrected with a small incision at the navel to access the area and place sutures to re-approximate the muscle. If that is indeed the problem, a smooth contour should result.
As you know it is not possible to determine the specific cause of the indentation without an in-person exam but it appears to be a muscle separation. Your belly button is located a bit high, which is an ideal situation for a mini-abdominoplasty (mini tummy tuck) with an umbilical float. That would allow for repairing the muscle separation without a scar around the belly button. If it is a muscle separation from pregnancy, it cannot be corrected with exercise.
Thank you for your question about your belly button surgery.
The photo suggests that this may be stretching of the umbilicus from the pregnancy, or stretch marks or a hernia or diastasis of the muscles in this area.
An exam will allow your surgeon to determine the cause -
The correction with depend on the cause.
Always consult a Board Certified Plastic Surgeon.
Hope you find this information helpful. Best wishes.
Those look like stretch marks to me. I believe they are indented because the skin is very thin and there is no muscle attached behind it in that area. There are some radiofrequency "lasers" that may work to tighten the skin, but I have been disappointed by the results. Given where your stretch marks are, I think they could be cut out surgically and sutured back together carefully, leaving a very slight scar above (or right on the upper border) of your belly button.
Your belly button may have been stretched to accommodate a large pregnant uterus and you now may have an umbilical hernia. You should be examined to see if this is the case and you may consider a hernia repair. This would be a surgical procedure. There are no non-surgical treatments for a hernia.