Naw...don't sweat the small stuff :-D
The bees will handle most all of the mistakes in the equipment you make. If my mistakes were only .125 inches, I'd be happy with it!!
Like the others said, maybe a little propolis, maybe some extra comb, a pain but not insurmountable.
And if the 1/8 is at the top or bottom of the box, then it is just known as a hive tool space!!