It depends on how sharply and squarely the rod was struck. If it was hit hard enough to delaminate the layers of Graphite from one another, it's probably going to go quickly, especially in an area that is flexed alot.

A past job I used to do was test graphite parts for aerospace use. The material is pretty tough as long as it remains intact. I have also done some damage growth monitoring on parts that were purposely delaminated and put through their paces and showed no significant growth through the course of the test. But there's always the other side of the story. If your graphite rod is hit hard enough to leave an impression on the surface or visibly separate the protective clear coat from the rod, it probably wouldn't be a good idea to use the rod until you could get it checked out.