If, as you say, it's minimal, I wouldn't worry about it at all. There are many guitars (even acoustics...) that are not symmetrically balanced anyway, so even if the wall mount was 'plumb', the weight could well be offset. I've never heard of a guitar neck being affected by being hung this way; they are pretty solidly constructed. If it's only an aesthetic thing, I'd leave it alone.
It would be possible to redress things a little, without taking the wall mount down, by winding a piece of cloth onto one side of the mount, as packing, to have the guitar 'plumb'; I'd surely not bother. Hope this helps.