Shoppers scattered and shops locked their doors following the attack outside McDonald's on High Street at around 9.30am on Thursday.
A 21-year-old man was arested after a 47-year-old suffered a slash wound to his head.
George Speight, from Goldthorpe, South Yorkshire, said the injured man had a slash all the way down his face.
Mr Speight said he had gone into the busy McDonald’s for a coffee when everyone suddenly rushed towards the front.
He said: “I turned round to see what the commotion was. There was a guy stood with a big machete, about 15-inches long.
“And then there's a bloke running towards me with his face slashed all down one side. The manager and me ran towards the door, we locked the door.”
Mr Speight said: “The next thing, the coppers have Tasered him and jumped on him.”
Asked if the man resisted the officers, he said: “He had no choice because they Tasered him and about eight people jumped on him.”
Mr Speight said the man appeared to have mental health issues.
“He didn't seem in the right frame of mind, at all,” he said.
Police said a 21-year-old man was arrested on suspicion of attempted murder, possession of a knife or bladed article and possession of drugs.
He is currently in custody awaiting interview.
The incident is not believed to be terror related.
The 47-year-old man injured in the incident was taken to the Northern General Hospital with non-life threatening injuries.