Can scar tissue/suture granuloma form internally under the nipple after a breast reduction with new implants?

It is impossible to accurately answer your question without a proper physical exam. There is not enough information to give you a proper response.
Scar tissue may form anywhere: thick or thin, painful or painless. Most surgeons use dissolving sutures when performing a lollipop mastopexy (whereas in a periareolar procedure, a permanent suture may be left in place).
Return to your surgeon for their opinion.
Best wishes.
Dr. Taranow