The pair came to blows at a New York Fashion Week party on Friday, which Cardi later suggested was because Nicki made comments about her parenting.
Nicki said on her Beats One radio show: “It’s so sad for someone to pin that on me, because I’m the bad guy and they know people would believe them.
“I would never talk about anyone’s child or parenting.”
Cardi B gave birth to daughter Kulture Kiari Cephus in July. She’d secretly married the father, Migos rapper Offset, in September last year.
The rappers seemed to be on good terms at the Met Gala in May
A feud between Nicki and the Bodak Yellow rapper has been simmering for a while, but got physical during the fashion week party .
The scuffle began after Cardi approached her rival over “lies Nicki was spreading”, celebrity website TMZ said.
She was allegedly elbowed in the face by a security guard, before throwing a shoe at Nicki, who appeared unscathed from the incident.
Cardi B was escorted out barefoot with a bump above her eye.
“The way they [party guests] passed by looking at this disgusting commotion, I will never forget. I was mortified,” said Nicki.
Seemingly talking directly to Cardi B, she said: “You’re angry and you’re sad. This is not funny and this is not about attacking.
“This is about getting this woman some help.”
Newsbeat has contacted Cardi B’s representatives for a comment.