Usually, your stitch gauge is going to be different than your row gauge. If you just have a few stitches too many, rip back and skip a few "holes" when you're picking up... if you have 5 too many stitches, skip 5 holes as you pick up along the way (space them apart so you don't have a big gap or pucker) and it should work out fine!
Congrats to you for doing a cardigan as your second project!
