You don't say if you suspect a problem. If you don't, this is unnecessary. If you do you are best of discussing this with your surgeon who knows what was done and has followed your recovery and healing. All the best.
In general this is not necessary. If you think your belly button is getting too small, you should discuss this with your plastic surgeon. For a couple of my patients who were concerned about the scar causing their belly button to be too small, a marble was helpful. But in one of them it got stuck and we had to remove it in the office, so be careful and check with your surgeon. Good luck to you.