Definitely don't worry about it - it happens - and probably has happened to most pilots at one time or another.
I once vomited all over my instructor when I was doing my PPL - and, understandably, I don't think he wasn't best pleased (though he was suitably sympathetic at the time...) Got over it though and now fly the 737...
Just stick with it, do be careful what you eat and give yourself time to adjust. Light aircraft do get bounced around a bit but when you've done a few lessons you'll be much more prepared for it and be concentrating so much on what you're doing you'll hardly notice.
Best of luck
