Chain brushes derailleur
Derailer  adjustment is easy - at least in theory. When it comes to fine adjustment you may find that you cannot easily get this problem fixed without making something else worse - i.e. its a compromise. Its a good opportunity to learn how to adjust derailers- make adjustments slowly, one step at a time, and count the turns so you can go back to the start if needed.

Given you should not be spending any time in this gear combo, and its not really doing any damage to the bike components, one option is to leave it alone and learn to switch to the smaller chain ring sooner. 

It is worth taking it back to the bike shop and seeing if they can tweak it, but do make it clear to them that you do not want to compromise gear shifts to get it fixed.