It's very normal to have a side that outproduces the other. You can try to nurse more on the side that produces less. It may or may not help. ;). Lots of lopsided women walking around;) makes bra shopping fun.
you can try to always start on the smaller side to increase it's production, but make sure you are draining the other side frequently enough as well...or maybe start on the smaller side two times in a row and then the third feeding start the fuller side...it's not uncommon for you to be 1/2 to a full cup larger on one side than the other anyway, it just becomes more noticeable when they are full of milk.
It's pretty normal to have one breast that produces more then the other. I did when dd was younger but they seemed to even themselves out after a few months. If it bothers you, try nursing on the smaller side more frequently to build supply on that side.