Nicholson advised the United States Forest Service in its initial and subsequent land purchases in what is now the Chattooga River Ranger District of the Chattahoochee National Forest. He and Arthur Woody are considered to be the two most important early figures in the history of the Chattahoochee National Forest.
In addition to being instrumental in the early land purchases, Ranger "Nick", as he was called, worked to prevent forest fires by purchasing bloodhounds to track arsonists and building the first fire tower in the area on Rabun Bald (second-highest peak in Georgia). He also played an important role in establishing telecommunications in the region, being responsible for having telephone lines run from Clayton, Georgia to Pine Mountain.