The lighter, thrown from the crowd, struck Ronaldo as he walked from the pitch at half-time of the Copa del Rey semi-final second leg at the Vicente Calderon on Tuesday.
Ronaldo, who scored two penalties in the first half, received treatment at the scene before returning for the second half as Madrid claimed a 5-0 aggregate win and a 2-0 victory on the night to progress to the final.
The Spanish Football Federation's Competition Committee revealed on Friday that Atletico have been punished, as a statement confirmed: "Impose upon Football Club Atletico de Madrid a sanction of a €600 fine for the breaching of Article 110 of the RFEF (Spanish Football Federation) Disciplinary Code.
"With the warning that hereon in greater efforts must be made to avoid such incidents and if they should occur, to identify the spectators involved, and that further disciplinary action will be executed should incidents of this nature repeat themselves.
"This resolution may be appealed to the Appeals Committee."
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