Behnezhad suffered a foot injury in the match against Slovenia in Week 1 and Karimi sustained a finger injury during trainings.
Iran will begin Week 2 on Wednesday with a match against Serbia.
Roberto Piazza’s men are also scheduled to face Argentina on June 27 and Germany and the Netherlands in the following days.
“It is normal for players to suffer minor injuries when participating in competitions like the Nations League,” Piazza said.
“This matter was investigated at the hospital and according to the tests that were done, there is nothing to worry about. There is no need to worry right now,” he added.