If you don't want to get marks after wearing sunglasses, you'd better choose light weight sunglasses and do not wear sunglasses for a long time. In fact, it is really difficult to avoid the marks on the nose if you wear sunglasses. If you do not want your nose get marks, seldom wear sunglasses or eyeglasses. Good luck.
Usually the heavy weight sunglasses with nose pad will of course leave the mark on your nose. The obvious reason may be the disposition of way you wear sunglasses. However, the best way to avoid the mark on your nose when wearing the sunglasses is to wear the sunglasses with light weight. You'd better choose the material of plastic or the panel. Then, you should keep in mind that not wearing it for a long continuous time, putting on and off in turn of several time. Thus, you may avoid the mark on your nose when wearing the sunglasses.