The boy's mother called police Friday, saying her son had found the needle while eating a slice of toast from a loaf of Bimbo brand sliced white bread.
The loaf had been purchased on Wednesday at the Stop & Shop Supermarket on Route 6, in Baldwin Place, in the Town of Somers.
The Stop & Shop Supermarket and Bimbo Bakeries were notified of the incident, as was the Westchester County Department of Health and the statewide Consumer Product Tampering database.
The family lived in Mahopac, N.Y.
Authorities are asking anyone with information to contact state police at 914-769-2600.