Wondering if I continue to massage scar tissue on my nose years after a rhinoplasty if it will continue to go down?

If you had rhinoplasty years ago, then you may need to get a steroid injection into the scarring to alleviate its prominence.  This is a simple procedure that can be done by your surgeon.

In general, scars mature and reach their permanent state at 1 year.  Unfortunately, I do not think massaging the scar at this stage will have any effect.  However, depending upon the location and nature of your nasal scar, there may be non-surgical options for improvement.  My recommendation is to see a facial plastic surgeon for a consultation.
Best of luck.