The thief is understood to have brandished a weapon and demanded money from Destinations Travel in Carlton Hill, according to the Nottingham Post.
The shop owner was taken to hospital for treatment of the head injury, but the police said nothing was taken in the incident.
A Nottinghamshire Police spokesperson said: “The suspect is described as white about 27 years old, around 5ft 7ins tall and of medium to slight build. He has dark hair which was slightly wavy or curly and about 2ins long.
"When he entered the shop he was wearing a grey cap with a logo on the front, a dark top and trousers and a yellow high visibility waistcoat."
