The incident happened at around 6.30pm on Thursday 6 September in Noel Street, Hyson Green.
A man aged between 30 and 35-years-old approached the boy and his mother.
Nottinghamshire Police have released a CCTV image of a man they want to speak to in connection with the incident.
More top news
Workers have announced six dates in June, July and August when they will strike.
A heavy police presence is expected ahead of a Britain First protest in this weekend.
Homeowners whose letterbox is either attached to a gate or on the outside of the property are warned they could be a victim of fraud.