If I am interpreting the trajectory of the nail correctly - point is pushing outward / slightly downward and forward - I don't see how it could possibly be a nail that was used to apply the toe plate. Edit:
That is, unless it was an incredibly long nail that was driven completely through the sole and the welt, into the toe box and then bent forward and pushed through the upper...which would be an egregious error by the craftsman.
I know very little about shoe construction (just enjoy wearing them), but perhaps one possible scenario is that it was an ill-placed tack in the construction of the shoe, that was an undetectible flaw until forced through the toe box by the pressure of applying the toe plate.
If such a thing is possible, I wouldn't consider that to be the fault of the person who applied the toe plate. Like an earlier post recounted in the case with a material flaw in his leather, it would simply be an unfortunate condition that coincidentally manifest itself in the context of the shoe repair.