It's not very clear what part of the image is the bug spot. I think it's the lighter area. A different frame capture may help. You can put the image directly on this forum by clicking the camera above and picking a file from your computer.
If the problem is indeed this lighter swatch you'll have to create some kind of a mask on an adjustment layer and try and fix the contrast. I really need a better shot, something with something recognizable in the background.
Okay here's the whole shot: You can clearly see it's the white area now... The image is at quarter resolution as otherwise the file size limit would have been exceeded Here's a shot from later on in the clip: The mark is less easily discernible in this image, but say for instance you were watching on a cinema screen...
Revision FX' RE:Fill --> Extract the luminance of the clip, mask it out a bit use the resulting comp as an input for the Area Fill effect, set its mode to blend edges, fiddle with the parameters, layer the result on top of your source clip using a blending mode like Color or Overlay. Won't bring back the detzails, but at least even out the discoloration...
Thanks Worked a treat