Keep the oil. It is most likely good it is cheaper because although they import it it most likely is made from a mix of olives and has been adjusted for oleic acid content so as to be ok in a plastic bottle. If that is what you can afford I will not judge that. All olive oils are subject to being adulterated with other oils, most people cannot tell so they do it and they will do it as long as the laws are as they are. This is a risk you take.
Are there any additional ingredients in the stiry fry past broccoli, oil and peppers? seasoning? a bad pepper theoretically can give you a solanine reaction but you would have to be super super sensitive and you would have noticed this before.
Drink lots of water and do not worry evaluate tomorrow and see how you feel. After some days give the oil a try and see what happens and let us know.