Almost 8 months post septorhinoplasty nose is sagging on one side, do I need a revision? (Photo)

 First of all, it's important to follow-up with your surgeon to manage the soft-tissue envelope over the nose during the healing process for the first year. This includes steroid shots and taping. At the end of one year, if the asymmetry is caused from a cartilage growth, this can be shaved down with a revision rhinoplasty procedure. 

It's really difficult to tell without preoperative photos and a better postoperative frontal view.  It's a question best answered by your plastic surgeon as he is the only one who really knows what took place.  Even if you do need a revision, it is best to wait at least 12 mos to allow the tissues to settle and heal fully.
Best of luck.