I just finished a beautiful cabled cardigan but after I sewed the buttons on and buttoned it up, the border curled a little - like the buttons were pulling the border and making a wavy result. I’m not making this clear.
I’m wondering why this happened.
Were you by chance using stockinette stitch?? 
If you use stockinette st w/o a stable border, like garter st, then your work will curl up. That’s just the nature of stock. st.
What pattern did you use? Do you have a pic of your work?
No, it was k1 p1 ribbing. I don’t have a picture, and I already mailed it to my sister. It didn’t look that bad but I wanted it to be perfect!!!