As an enthusiast OCer personally I would get the CPU replaced. The thermal paste if used as a filler will not perform as well as the metal material it would have replaced in the chipped hole. But really it depends on how much of an enthusiast you are ,and arguably it is a small chip and so will have a very insignificant effect.
If your not overclocking it will be fine, it may create a hot spot on your heat spreader and raise your CPU temp by a margin of a margin of a margin (extremely small), but will not effect stability or performance.
As an overclocker I would try to squeeze as much ghz as poss out of it and would demand to have a perfect CPU, but again I'm a anal enthusiast and a perfectionist ha.
Source: I'm a professional mechanical engineer (have experience with thermal analysis)