The real question is, “Why would you risk it?” Rhinoplasty (nose job) is a very complex surgery, creating a balance between cosmesis and function. The sutures (stitches) used can barely be seen with the naked eye. Irrigating inside the nose early on can not only affect the sutures themselves, but prevent the wound edges from healing correctly in the early postoperative period.
If you’re going to undergo facial surgery, keep one thing in mind: You can’t hide it! Moral? Follow the instructions given by your surgeon. There is solid logic behind them.