What is this bug and should I be concerned?
It's a woodlouse.

Mostly an outdoor bug, generally beneficial, but may bother some plants. 

They are generally not a big deal in houses, although not pretty. Wikipedia comments


  Woodlice can also invade homes en masse in search of moisture and their presence can indicate dampness problems. They are not generally regarded as a serious household pest as they do not spread disease and do not damage sound wood or structures.


(When I was a kid, we called them potato bugs.)