Ever go to a theme park and walk around all day in the heat?
How about lifting a box that's too heavy, or a wet dog that struggles and jerks you around as it slips from your arms?
Maybe it's a weather pattern that spurs a sinus headache.
Pick a body part from the waist up and one from the waist down. Now add a pain and write two short scenes. Remember to show the pain not just tell it.