Hi, you can open a startup on any idea you have. It does not need to be about what you are studying. If you are unsure about how to actually build an startup there are many courses available online which will give a kick start to your career. You can study and do this on the side as well. Let me remind you that setting up an startup is very difficult and it might hinder with your studies. All the best! If you still have doubts please feel free to comment. Hope this helps.