syndrome. Try stretching and massaging the glute on the side of which you have sciatica and see if that helps relieve the symptoms. If you have sciatica down into the foot, most likely it is disc related, which, with proper treatment, can be resolved, and if not, you may need to get a surgery consult.
Most likely it is not a growth problem. It could be several things, but your rib cage could be off center causing one side to appear broader. Are you left handed or do a day to day activity that causes you to use your left shoulder more? That could cause extra muscle built on that side.
I would really have to do an evaluation to see it there was any cause for concern, but most likely it is nothing to worry about.