Exposed copper on PCB
That copper is most likely the ground fill unless there was a trace
  there before.   If there was a trace there as long as you did not
  damage the trace you should be fine (if it doesn't touch anything that
  wasn't already connected to that trace).   If its just ground (what it
  looks like) you should be fine as long as it doesn't touch anything
  that's not ground.
  
  If it isn't touching anything you should be fine.   If you're still
  worried about it just cover it with some glue to make extra sure it's
  insulated.    Its right next to exposed pads anyway though so thats
  probably not necessary (anything that would touch that part would
  touch the adjacent pins as well).
  
  Just make sure if you melt the solder on those pins again that it
  doesn't jump and connect itself to the exposed copper (as it looks
  like the exposed bit is pretty close to two of the pins).   Also
  double check it with a multimeter to make sure you haven't already
  done that... just check to make sure the exposed part is ground and
  unless either of those pins are ground you should not be reading
  continuity between either of the pins and the exposed pad.   If its
  not accidentally connected now and you leave it alone it should be
  fine.


EDIT:

You can tell from this picture that the exposed copper is ground:



So all you need to do is test with a multimeter to make sure neither the 4th pin from the bottom (of this picture) or the 5th pin from the bottom are connected to that exposed spot.   If they are not then you are all set (put some glue on it for ease of mind if you want).   If they are connected then it is most likely a solder bridge; use a desoldering wick to disconnect the pin from the exposed copper.   From this picture though (although it is blurry) I do not think it is bridged.