A Bronx infant has tragically died about a week after her mother’s boyfriend allegedly beat her so badly that doctors needed to remove a portion of her skull.

Imani Mitchell, 1, was rushed to Harlem Hospital in critical condition after Jerome Thomas – who was watching her the evening of Aug. 28 – allegedly “struck the child twice on the side of the head with a ‘heavy hand,’” causing her to cry, according to cops and prosecutors.

The helpless infant suffered “extensive subdural hemorrhaging on the right side of her head resulting in swelling and intracranial pressure causing brain herniation,” and had to have surgery to remove a piece of her skull, the criminal complaint revealed.

Imani was placed on a ventilator and other life support measures – but ultimately doctors were unable to save her.

The toddler was pronounced dead at the hospital Friday, and her death ruled a homicide, according to the NYPD.

Thomas,19, was initially arrested on Aug. 29 and charged with felony assault, reckless endangerment and endangering the welfare of a child, according to court documents.

The teen has since been ordered held without bail on Rikers Island, as his charges may now be upgraded pending a grand jury indictment, law enforcement sources said.

The fatal beating happened around 9:30 p.m. inside the apartment on Union Avenue near East 152nd Street in the Woodstock neighborhood, after Imani’s mother left her in Thomas’ care, according to the complaint.

He is next scheduled to appear in court Sept. 18, the DA’s office said.

Neighbor Nicole LaCroix previously told The Post the couple and the little girl were new to the building.

“I spent a little time with the mother, and I guess the boyfriend one night, just because they were new to the area, and we were just showing them where some of the stores are and different things like that,” said LaCroix, who recalled spending time with the infant. “Being helpful, as a neighbor, because I’m a little older than the young lady.

“I held the baby, you know, because we spent a little time with each other. She was playing with my phone – she was an active one year old.”

LaCroix said her daughter heard “arguments” coming from the trio’s apartment, and she wished she would have “stepped in and helped.”

“They fight every night. [I’ve heard] them argue every night since they moved here … ‘F–k you, b–ch.’ And ‘Get the f–k out,’” she said.

“Several times she put his clothes out, but they’d be back together the same day.”