It follows an incident with Roxanne Pallett on tonight's show, where the pair were messing around.
Ryan hit Roxanne, prompting her to complain to Big Brother.
She said in the Diary Room: "I need to speak to a producer.
"I'm just a little bit in shock. I went from being upset to angry now. He actually punched me like a boxer would punch a bag. It wasn't banter, it wasn't a joke.
"I can't believe you're letting someone stay who's done that. It's not okay."
Big Brother replied: "Big Brother takes something like this very seriously."
Ryan was called to the Diary Room and told: "Before you entered the Big Brother house, rules regarding unacceptable behaviour were explained to you. Big Brother has called you to the Diary Room because you have broken this rule."
Recalling the incident to Ryan, Big Brother added: "Whether you intended to hurt Roxanne or not is irrelevant."
Ryan replied: "There was no malice or hurt or anger in anything I did but I am sorry, I do understand."
Big Brother issued the soap star with a formal warning and added: "Any repetition of this behaviour, Big Brother may have no choice but to remove you from the house."
Later, Roxanne asked Big Brother to move to the spare bedroom.
"I'm suffering and having to alter my experience because someone else was violent," Roxanne cried, "I can't believe you're letting him stay."
Viewers watching the episode were NOT impressed with Roxanne's reaction to the incident.
Many claimed she was trying to get Ryan kicked out, with one writing on Twitter: "Roxanne is a complete and utter drama queen. It’s a disgrace what she’s doing now #CBB"
Another posted: "Roxanne is an insult to anyone who’s ever been punched by a man. Disgusting. #cbb"
And sharing a clip of the incident on Twitter, @LJay815 wrote: "SHE DIDNT EVEN FLINCH!!!!! #cbb @bbuk"
Elsewhere in tonight's show, housemates complained about Roxanne's 'attention seeking' antics.
"There's certain moments where I can be around her and there's certain moments where I need to go," Gabby said.
Hardeep commented: "She's a sweet girl who means well but everything's the Roxy show."
Nick added: "It's a bit ridiculous Everything that she does is attention seeking that's really really sickly. That's the only taste it can leave in your mouth. There's a certain amount of insecurity, she's playing to the camera. She's trying way too hard. Can anybody be like that in real life?"
Meanwhile, Dan and Ryan took a very cold bath together, Roxy made a very gruesome discovery under the coffee table and Ben told Roxy he loves her.
Celebrity Big Brother 2018 airs nightly at 9PM on Channel 5.