It is very common after gynecomastia reduction surgery to have scar tissue from behind/beneath the nipple. When the initial gynecomastia problem is relatively small, any nipple scar tissue formation can leave one with a still persistently nipple protrusion problem. In the first year after surgery (really the first six months) steroid injections can be very helpful in breaking down any scar tissue formations.
After one year the success of steroid injections to reduce prominent scar tissue diminishes considerably as the bonding of the collagen in the scar tissue becomes very mature. There is no harm in doing further steroid injections but be aware that the success of them at this far out from surgery may not be like what had occurred earlier after surgery. Should this fail you should consider a small revision through an open incision under local anesthesia as an office procedure. This can remove the problematic small area of the scar with little risk of recurrence. I have done this numerous times in secondary areolar gynecomastia reduction surgery.