Discomfort is the feeling of irritation, soreness, or pain that, though not severe, is annoying. Every year, people who get a cold or the flu experience a few days of discomfort.
The noun discomfort is good for describing situations when you aren't quite in pain, but you don't feel very good. Things that cause discomfort include a dull toothache, a blister on your foot, and a terrible mattress. Discomfort can also describe embarrassment, like the discomfort you'd feel if you suddenly realized you were in the wrong classroom.