The urgent move is a misnomer. *The* urgent move is always the one that's supposed to be played. No matter if it's a big or small move with regard to territory or thickness. The usual rule of thumb "play the urgent move, not the big move" refers to the smallish moves that typically don't get played because they seem small.

Like so many cancers, small things can compound if not taken care of. While you can put it off for now, or another move or so, if the opponent catches your miss before you do about this small but vital matter, then you'll be in trouble.