Any time you change your knitting style it's almost like learning anew. Try switching which hand you use to work your computer mouse? First you start out feeling like you are all thumbs, but eventually you get the gist of it. After a certain amount of time. you will begin to develop a more even tension.
If your piece is worked in wool or a wool blend you'll probably be able to fix any bumpiness with a bit of good blocking. Cottons and man made fibers can be a little more stubborn, but it a chance anyway.