Yeah, get aftermarket side steps. The genuine Nissan ones are POS. They do not extend far enough to cover the body panel just in front of the rear wheels, hence you get stones flying and hitting that area.
Took my titanium to Kangaroo Island for 2 days. Travel about 160kms of dirt road at around 80km/h and came back to Adelaide to find that there were stone chips at the underside section that you've mentioned.
An aftermarket side step would extend and cover all the body panels from the front wheel to the rear wheel.
Or you could paint on some hard rubber protection just at that little area. My car is black so it's easy to paint some black rubber stuff on.
