I don't want to sit by people who smell like smoke
Is there a reason why you don't want to sit next to people who smoke?
Because it makes my head hurt.
Putting your health at risk because of someone else's secondhand smoke is definitely something you should avoid. If you are getting headaches from the smell, don't feel bad about avoiding the people!
Yeah, I will be in a safer place.
That is a good thing to go ahead and move for your health and your sanity. It will make you feel a lot better to do.