This sounds like trauma to the marginal mandibular branch of the facial nerve on the side that does not move. It is most frequently a temporary problem that will disappear over several months. It should be discussed with your surgeon.
A related discussion,
crooked smile was started.
Wow, that's great news!! I'm so happy for you. I also was/am very swollen. The doctor said I started swelling on the operating table. I will start exercising the "fixed" side of my face now. Thanks so much for the encouragement.
At the end of week 3 my swelling is subsiding and my crooked smile is almost straight. I was swollen more (and tighter) on one side of my face than the other for the first 3 weeks - when I would try to smile, I looked like I had had a stroke on one side of my face. What I found that helped my situation was to exercise my face. I would actually force the opposite side of my mouth to stretch outward (not with my hand but using my facial muscles). In other words, I forced the muscles on the "fixed" side of my lip to make me look like I had had a stroke on the opposite side of my face. I don't know if it was the swelling subsiding, the nerves regenerating, or the facial exercise, but at the end of week 3, my crooked smile is straight. And when I say "crooked," I mean it was crooked! My bottom lip went to the far right and actually opened outward - it looked terrible and I was worried to death! Yesterday my son said, "Mom you are no longer talking out of the side of your mouth!" So don't be discouraged - time will take care of your problem ... I had a lot of swelling and some people keep their swollen face longer than others. Exercise the "fixed" side of your lip forcing it to widen, and I think you'll see positive results in a week or two. Good luck to you!
I had the same procedure on March 18, 2011 and am having the exact same problem. I went to a reputable surgeon and he said that he has seen this before and has never seen one that didn't heal properly. However, he advised that sometimes it can take up to six months. Please let me know your progress. This is very discouraging - I know.