Trains were briefly operating on the same track between Cermak and 47th, however, full service resumed with residual delays at about 4 p.m.
At about 1:15, the man was riding a bicycle on the 35th Street station platform when he lost balance and fell onto the track level just as a train was entering the station, according to the CTA.
CTA officials said they do not allow the operation of a bicycle or any type of wheels on the platform.
The station is located near Guaranteed Rate Field in the city's Bridgeport neighborhood.