Power has been restored to the remaining areas that were plunged into darkness by the fire in the Back Bay Tuesday night, NStar said this morning. But the company also urged people to call if their lights still weren’t on. “We restored power overnight to the remaining areas affected by the outage,” NStar said this morning in an official tweet. “Please call us if your power has not returned.” An NStar spokesman didn’t immediately return a telephone message and an email seeking comment.