LOL

Its a result from over tightening. You must have gone pass the torque specs prob by stepping on it to tighten to this point.

Its easy to remove. Use a big breaker bar, and ur foot if you have to. If you use ur body weight make sure that you have the breaker on a angle of about 45 degree with the handle end pointing to the floor to avoid stress on your stud.

But as a result of over tightening, expect your stud to snap in future.

next time just screw the nut on till it stops then give it another 1/4 turn thats enough to secure it.