I can only offer an opinion as a student aeronautical engineer, thus I could be completely wrong...
Whilst it does look like a fairly significant dent, the chances of it actually being serious are quite slim as I believe the skin surface of a wing/stabiliser is quite thin (hence various other ripples through out the aircraft surface due to constant changes in pressure during flight) and not load bearing, such as the struts and beams inside the wing. So whilst that some sort of eventual repair might be needed if it is a dent within the surface, it may not occur until the aircraft is next due in for maintence.
On a side note, great picture. I have noticed that Lauda Air fly in to BFS on Saturdays so I have been pondering on weather or not a trip to BFS would be worth while to capture the airline.