It's very hard to say. It seems that so many "ghost in a picture!" is easily photoshopped now a days, but I don't think you or anyone photoshopped it.
It could be a ghost, or a dirty lense? perhaps smoke but I am leaning torwards ghost if the lens were not dirty, no smoke in the area, and not photoshopped.
If it's a ghost, that's awesome tho!
I'm a huge believer in ghosts but I am totally iffy about pictures online or EVPs, I wish people that say oh there's a ghost in the picture but it's really not a ghost can stop putting them on the net. :l