Type 304/316 stainless steels are not terribly notch sensitive IIRC. If it bothers you, however, you should know that the the spoke wouldn't be appreciably weakened by the small loss of metal, but rather by the imperfection, which could act as a stress concentrator. Simple fix is to polish the spoke smooth with 0000 steel wool. Once smooth the spike will have essentially all of its original strength unless the scratch were very deep.