Raheem Bailey was beaten by a group of children at school on Tuesday, Shantal Bailey said.
Ms Bailey, 28, said her son tried to escape school but got his right-hand ring finger caught while climbing a fence, and it later had to be amputated.
She said Raheem has faced “racial and physical abuse” since he started secondary school at Abertillery Learning Community in South Wales in September.
The family have received a flood of support since Ms Bailey described her son’s plight in a GoFundMe page she set up last week to support his recovery, which hit more than £85,000 in donations by Sunday.
Anthony Joshua, Jadon Sancho and footballer Ashley Williams have sent private messages of support through Ms Bailey’s Instagram.
Ms Bailey said Raheem also received messages from football manager Chris Hughton, pundit Gary Neville and Olympic BMX biker Kye Whyte.
US basketball player Gerald Green, who forged a hugely successful career with nine fingers, has even set up a call to speak to Raheem directly, she added.
Speaking to the PA news agency on Sunday, she said: “Here’s so many people just in different places that have been so generous, and I did not expect what has happened so I am truly, truly grateful for it.”
Describing what happened to Raheem, she said: “While he was climbing over, he had a ring on, and his ring attached to the fence and it ripped but also broke his finger.
“Basically, he was running away because he was so tired of being picked on every day.”
Ms Bailey said her son was “truly brave” and had been “in utter agony”.
“The whole time [he was] telling me ‘I’m sorry, I’m sorry mummy. I just couldn’t, I couldn’t stay there, like why does no-one like me?’
“These are things that my child, while being in pain, is constantly having to ask me, ‘mummy, why does no-one like me? Like why? Why did they pick on me?’”
On how he is doing now, she said: “Occasionally, he’s feeling very down and I have to talk to him and make him understand that no matter what, I will be there.”
But she added that the support has “really put smiles on his face” and is “making him pick his head up”.
She said of the fundraising: “He has got ideas of how much it’s growing and he is really, really happy.”
She also said the messages he has received mean so much, as people tell him “how strong he is and that this does not define him”.
“It’s been amazing because it’s like another kind of boost, of ‘there you go, you see there is mean people but there’s also a lot of nice people’,” she added.
“I am truly, truly, truly grateful and if it can do anything by, you know, raising awareness for racism, bullies, whatever.
“There’s so many people that get targeted for differences that they don’t have control over, whether or not it’s a disability, whatever it is, it can be tackled, and so things like this does shed light on it.”
Speaking about the wider issue of bullying and racism in schools, she said: “Why should I send my child into school to be a punching bag?”
“I just don’t understand, something needs to be done, I think it needs a conversation to be had.”
Growing tearful, she said: “It is difficult, as a mum, having to tell your child that people might not like you because of your skin – not because you’re mean, not because you’re horrible, but just because of the skin he was born into.”
The Welsh Government said: “We condemn bullying and racial harassment in any form and expect allegations and incidents of bullying and racism to be fully investigated by schools, with appropriate action taken to address the matter and prevent further instances from happening.”
A spokeswoman for Abertillery Learning Community told Wales Online: “We are currently working closely with Gwent Police and the local authority to establish the full details of the incident.
“The wellbeing and safety of our pupils and staff remains of paramount importance.”
A Gwent Police spokesman also told Wales Online: “We received a report of an incident at a school in Abertillery around 1pm on Wednesday, where an 11-year-old boy was injured.
“A multi-agency meeting has taken place and we’re working with the school as part of our ongoing inquiries.”
PA has contacted Gwent Police and Abertillery Learning Community.
Published: by Radio NewsHub
Written by: ES1
His son Lachlan will replace him.