Without actually seeing it, my guess is that your hole is a result of the stitches pulling out of alignment. I would use a tapestry needle and some yarn to sew a stitch at each end of the buttonhole.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry