be a square peg

be a square peg (in a round hole)

To act or think differently than most people, especially when it causes one to not fit in or be comfortable with others or in a particular situation. It only took three months to realize I was a square peg in a round hole at the firm. I guess I just don't buy into the whole corporate hierarchy of modern business. When the man in the fancy suit walked into the biker bar, it was obvious that he was a square peg.
See also: peg, round, square
Farlex Dictionary of Idioms.

be a square ˈpeg (in a round ˈhole)

(British English, informal) not fit well or easily into an organization, a job, etc. because you are different: I don’t have the right personality for the job. I feel like a square peg in a round hole. OPPOSITE: in your element
See also: peg, square
Farlex Partner Idioms Dictionary
See also:
  • be a square peg (in a round hole)
  • a round peg in a square hole
  • a square peg in a round hole
  • round peg in a square hole, a
  • square peg in a round hole
  • (one's) scene
  • a bed of roses
  • change (someone's) mind
  • aint
  • ain't