No, not a good idea. The injection of any material can cause scarring. It can hamper the normal growth and/or make the rhinoplasty more difficult.
If you were to still proceed I would certainly stick with hyaluronic acid injections only, i.e., Juvederm and Restylane.
The bigger concern I have is that why the child is so conscious and upset about it. At 12 years of age if the child is so concerned about the nose it might point out to some underlying unaddressed pscyhological issues. If there is any chance this could be the case, please make sure you get the proper counselling for the child.
Regards

