I can think of two possible reasons for your symptoms. One, you smoked (including second-hand smoke) more than waht is usual for you and an excess of nicotine
in your body has caused the light-headedness. Secondly, it is possible that you smoked marijuana or were passively exposed to it. Of course, both may be true as well. In addition, heavy drinking may also contribute to the same. But there is no need to worry as the symptoms will improve and you will be fine in a few days.