The incident happened in Walm Lane near Willesden Green station just after 9.05pm yesterday (April 1).
Officers say the victim was driving his car when he was followed by a suspect in another vehicle.
It is believed that a crash took place, and the man ran into the restaurant where he was stabbed.
The victim then took himself to hospital where his injuries were assessed as non life threatening.
No arrests have been made as police enquiries into the circumstances continue.
A spokesperson for Metropolitan Police said: “Police were called at around 21:06hrs on Tuesday, 1 April, to reports of a stabbing inside a restaurant in Walm Lane, Willesden.
“A man in his 20s then self-presented to hospital with stab wounds. His condition is not life-threatening or life-changing.
“It is believed the victim was driving his car when he was followed by the suspect in another vehicle. A collision took place and the victim ran into the restaurant where he was stabbed.
“No arrests have been made at this time but officers continue to follow all available lines of enquiry.”
