If it's made from wool, you can try shrinking it in the washer with hot water, but keep an eye on it so it doesn't get too small. Otherwise, reknit with smaller needles and/or fewer stitches. He's a good sport about it!
"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