Could be an arrow wound, but I doubt a deer would survive a shot that hit there... from a treestand at least. IMO, it looks like a bug flying in the air between the cam and the deer. To me, it looks like there is a shadow behind it. I could be wrong, but I know I get a lot of flying insects in my trail cam pics at night. Hopefully you get some more pics of that deer. It's tought to confirm anything after just one pic.