Most of the colonoscopies or endoscopies end up normally without any complications but sometimes colonoscopy
can damage the colon.This may result in bleeding or infection or some perforation.
But in such cases you get bleeding through anus,fever
if infection is there and gradually worsening pain abdomen,if here is some perforation.
Since you don't have above mentioned symotoms or signs,you appear to be normal and remaining discomfort should settle in few days.
As far as lightheadedness
is concerned,it could be due to the effect of sedatives given during colonoscopy,which shall also become alright very soon.
Every thing appears normal but if your symptoms deteriorate,less likely as already it is more than three days since your colonoscopy,then you are advised to go to ER.