If the instructor was flying the plane and you were getting sick, don't worry about it. That phase of the instructor flying is very short. I've got over 10,000 hours between being a pilot and loadmaster in the air force. Put me in the back of a C-130 on a low level and I start feeling sick after 45 mins. I never have a problem when I'm up front though.
Try flying first thing in the morning. It's usually the smoothest part of the day. If the instructor is jerky on the controls that could be a problem too. Maybe try flying with a different instructor. Some of it may be due to nerves.