Russian bantamweight Vladimir Nikitin will not box American Shakur Stevenson after being left bloodied by Conlan.
"The injury suffered by Vladimir is too serious," said Russian official Igor Kazikov.
Stevenson will fight Robeisy Ramirez Carrazana in the final after the Cuban beat Uzbekistan's Murodjon Akhmadaliev.
Nikitin, meanwhile, will still receive a bronze medal.
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Belfast boxer Conlan said after Tuesday's contentious decision that his Olympic dream had "been robbed".
Nikitin's face was badly bloodied after the quarter-final, which most observers felt had been conclusively won by the Irishman.
Immediately after the bout, Conlan made clear his annoyance at the verdict in an expletive-filled live TV interview with Irish broadcaster RTE.
Thursday's development may increase the the pressure on amateur boxing's world governing body, Aiba, which has faced criticism from boxers and coaches in Rio after a number of contentious judging decisions.
On Wednesday, the international body announced that it had dropped a number of officials after a review of their decisions at the Olympics.
Aiba said that, after 239 bouts in Rio, "less than a handful of the decisions were not at the level expected".
The body has admitted it is in a "transition process", but said results of bouts already contested will stand.
The boxer who controversially beat Ireland's Michael Conlan in the Olympic quarter-finals has pulled out of his Olympic semi-final because of injury.