The Occupational Safety and Health Administration announced the fine Thursday against Wisconsin Central Limited railway.
OSHA says the injury occurred in Manitowoc. A message left with OSHA seeking more details was not immediately returned.
The agency says the conductor was injured during his 60-day probationary period. The injury was reported that day but not before the end of his shift. The company terminated him on the last day of probation, saying he failed to report the injury promptly.
OSHA ordered that the man's job be reinstated.
A CN spokesman says the railroad disagrees with OSHA's ruling and is considering its appeal options.