Yes. Most moms notice at least a little difference between the milk supply and size in left breast versus right breast. (You know how one of your feet is a little longer, and your hands have slightly different ring sizes? Same thing.) If this isn't causing you any problems, then don't worry about it. You don't need to do anything.
But if you feel that one breast is noticeably smaller, you may feel the need to increase your supply on the lower producing (i.e., smaller) one. To do this, you can try nursing baby more often on the smaller side or pumping the smaller side after or between feedings. This should help to even out your milk supply within a few days.
Be sure not to neglect the other breast though. If the larger breast becomes uncomfortably full, express a little milk to ease the pressure.