First I take a lightly dampened (almost dry) rag with a teaspoon of Fast Orange hand cleaner and completely clean all up and down the shaft to remove all chalk and dirt. Next I rinse out my rag and remove as much water as possible, then stroke shaft again to remove any residue. Then I immediately take a clean dry cotton rag and stroke up and down quickly to dry off shaft, this way I begin with a clean shaft to remove the nick.
Next I take a Q-tip and wet it with hot water. Then I lay my shaft on a counter top where it can't roll and block it into that position with the nick on the top side, then I set the Q-tip with the wet end on the dented area for several minutes. Finally I check the shaft and see if I needs to roll a little and repeat steps above. When I am happy with the dent removal then I sand (400, 600, 800, 1000, 1500, 2000, 2500 as needed), reseal with Cue Wax, burnish and play until it happens again. I use a lathe turning around 1,500 RPMs, but you can do it by hand with similar results.
Hope this helps,
John