A similar thing happened to my wife's bumper. No matter how I tried I couldn't really conceal it so I used these. I suppose it depends where the ding is. I put two on. One on the opposite side to the ding so it matched.
They are self adhesive and have never come off even when washing her car, they have been on for about 18 months now, but if they did you could always glue them on. I was more than pleased at the result as was the wife and they didn't look odd at all. Although small, the black filler always noticed.