The incident happened at Pitta Patta Nursery in St Germans Road just after 5pm on July 2.
Officers attended and the boy was taken to hospital.
He has since been discharged.
In a letter seen by the News Shopper, Ofsted has now suspended the registration of the nursery.
The period of suspension has been put in place for six weeks from July 3, 2025 to 13 August 2025.
Ofsted said continued provision of childcare at the nursery “may expose children to a risk of harm”.
The purpose of the suspension is to allow time for enquiries to be made and steps to be taken to eliminate or reduce any risk of harm.
It added: “Pitta Patta Day Nursery Limited must not act as a registered childcare provider while suspended.
“It is an offence for a person registered on the Early Years Register or the compulsory part of the Childcare Register to provide childcare which requires registration, while suspended.”
The suspension is a temporary measure which will be reviewed and possibly lifted if it finds that children are not at risk.
It explained: “We will write to you if we lift the suspension and Pitta Patta Day Nursery Limited can resume providing registered childcare.
“We will also write to you if we are unable to complete our enquiries and/or take steps to eliminate or reduce any risk of harm within this initial suspension period and we impose a further period of suspension.
“If as a result of our enquiries, we or the provider need to take action to meet the requirements, we will publish an outcome summary on the setting’s page on our reports website reports.ofsted.gov.uk.”
“If we consider that the provider is no longer suitable to provide childcare, we may take steps to cancel the registration while the suspension is in place.
“If the registration covers more than one setting, cancellation will apply to all settings in that registration.”
A spokesperson for Metropolitan Police said: “Police were called by the London Ambulance Service to St German’s Road, SE23 at 17:09hrs on Wednesday, 2 July following reports of a child sustaining a serious injury.
“The 4-year-old boy was taken to hospital and has since been discharged.
“Enquiries remain ongoing.”
We have contacted Pitta Patta Day Nursery and Ofsted for further details on the incident.
