Don't be. Just be vigilant when it comes to chips. Buy some duplicolor with the brush and repair them right away.

 

My 2010 also started rusting on the back side from road debris/rocks pelting it and I noticed it and removed the bumper and sensors, and then lightly sanded and put rocker chip guard on the back side to slow it down and protect it.
Since your bumper is painted it is prob best to just pick up a new one and put some protection on the back side to help keep it from happening and rusting through again.