My advise to you is to carry on, with a but though. If you can get the chance to go up without doing training for a couple of flights (maybe an hour and a bit or so) to get your legs back. This is easy to do, for example there is always a full load check being done, or a CPL trainee doing a cross country flight that they may like company on.
If you know that you get airsick now, you will tend to focus on that during the lesson, and may very well miss the point of a lesson, and then will have to do it all over again!
We have all gotten airsick at one time or another, and its nothing to be worried about. :P
Keep yer eyes to the skies and remember, oxygen is only a myth!