A drug user threatened to stab his former probation officer and got out a needle, a court heard.
Sam Sharpe, 22, bumped into the man as he left Nottingham's Rock City with friends after a gig on April 6.
At first he asked if he had any change, referred to him by name and told him about his present situation using drugs.
Sharpe said he was begging and did not know what to do and "explained his troubles", said Stuart Pattinson, prosecuting.
"He said no one else was taking him seriously. The complainant was not his supervisor any more."
The victim told Sharpe he had moved to the divisional sex offender unit.
Sharpe seemed to misinterpret "sex offender" applied to him which was not the case, said Mr Pattinson.
The man walked down Goldsmith Street, while the defendant followed shouting at the top of his voice he was "not a sex offender".
He shouted in the man's face and threatened to assault him, grabbing his hood and taking a swing at him which missed.
Sharpe had his back to a wall and went through his pockets, telling the man "I'm going to stab you now" and "I've got a sharp (needle)".
The man ran and raised the alarm with police.
After Sharpe's arrest, he pleaded guilty to affray at Nottingham Crown Court and was locked up for 12 months.
Judge Steven Coupland, who sentenced him, heard a victim impact statement from the victim, describing how the man "feared for his safety" and had worked with the defendant for a lengthy period of time.
The judge told Sharpe, of no fixed address: "You threatened to stab him with 'a sharp'. you produced a needle given to you as a kit in case you overdosed on opioids. You were an intravenous drug user."
Mitigating, Katrina Wilson, said: "Through me he wishes to apologise to the complainant. He shouldn't have behaved like that and he a acknowledges that."
She said he has his own difficulties. Since the age of 14 he has been homeless or residing at various HMP establishments.
The judge was impressed that since Sharpe has been in custody he has done all he can to try and change and is on a Methadone prescription and is trying to address mental health issues.
