Without seeing it happen it's hard to tell.
How much tension is your hand under? Have you tried slowing down and concentrating on relaxing while using minimal movement? I find this helps me a lot with right hand issues of different kinds. I know it sucks to play really slow but after a while I can get into it and it really does help me to relax and correct problems.
How much does it affect your playing? Does it cause you to miss notes/strings? Is that finger out of control timing wise? If these are not and issue, and it is just the aesthetics of how you think your hand should look when playing I wouldn't worry too much about it. The important thing is are you getting what you want out of the instrument.
a little story:
I remember Missy Raines when she was quite young playing with the "Young Blades of Bluegrass"...Although excellent on the Bass she couldn't keep her tongue in her mouth while she played. It waggled and wiggled and waved all over the place during their shows...it was quite a site, and distracted from what the band was doing on stage. She has since grown out of that and is a top notch musician and performer. Many players have physical quirks that happen when they play, or problem areas they have to work on regularly. Myself I have trouble hitting the string with my first finger, doing a straight forward roll, and I sometimes drool on my banjo when concentrating hard.