What a coincidence -- I just went to the eye doctor today! I'm near-sighted too, plus I've got some astigmatism.
I think you could go either way. If you can read okay but just have trouble seeing things in the distance, you can probably go without glasses while knitting. In my case, even though my near-sightedness got worse since my last appt and I got a stronger prescription, the doctor recommended that I wear my older (slightly weaker) glasses when I'm in front of the computer since I don't need as much correction up close. Since your vision is probably not too bad, you can probably see fine up close without glasses at all.
Of course, I don't think it would hurt if you wanted to wear your glasses all the time either. (Imagine what a pain it would be if you got contacts!)
Try it both ways and see!