The 23-year-old ignored orders from the Italian to allow strike-partner Aleksandar Mitrovic to take a late spot-kick when the scores were goalless at Craven Cottage.
Jonas Lossl saved Kamara's effort and though Mitrovic fired home a winner in stoppage time, Ranieri admitted he "wanted to kill" him after the miss.
Kamara was threatened with being dropped for the trip to Arsenal on New Year's Day but Ranieri says that after a heartfelt apology to the rest of the squad the episode is over.
"Now everything is finished," said the Italian.
"He came to me after I called all the squad, all the people around us, and they (all) apologised. For me it's finished.
"The team is the first in my idea, if I need him he continues to play but he has to improve what I ask.
"He's a good guy and I hope also the fans are behind him and all the team."
Ranieri's criticism was followed by swathes of racist abuse on social media directed towards Kamara.
The West London club have slammed fans for their reaction and have pledged to take the "strongest possible action" against those offenders.
Victory over Huddersfield ended a seven-match unbeaten run for the Whites and they could climb out of the bottom three if they overcome the Gunners
Alfie Mawson will be missing after suffering a knee injury against the Terriers but Andre-Frank Anguissa is back in contention.