Stephen Nelson, now 19, carried out the attack on the woman before targeting her son with pal Andrew Calvert on December 8, 2020.
Newcastle Crown Court heard the incident took place when Nelson attacked the woman who had approached him when she saw him become angry.
Miss Recorder Davies said: "You two defendants (Nelson and Calvert) were outside a fish and chip shop in Horsley Hill Square in South Shields.
"On that day at the same time was a man and his mother, you all knew each other.
"It started with the male going into the chip shop, Nelson you followed while Calvert stayed outside."
The court heard Nelson was asked to leave by staff and could be seen on camera leaving the chippy hiding a metal bar in his possession.
However, instead of leaving the scene he produced the bar and began to strike the shop's entrance with it.
Concerned about her son inside, the woman approached from nearby and tried to discourage Nelson which led him to launch an attack on her.
The judge added: "The most serious aspect of this unpleasant incident is you Nelson got your metal bar and you struck her on the head.
"It caused a nasty two or three inch cut to the back of the head causing her immediate pain and injury."
Shortly afterwards, Nelson, accompanied with Calvert at this point, targeted the son who had since left the shop by throwing punches towards him.
The mum was left needing hospital treatment for the cut which required cleaning and stapling following the incident.
In a victim statement, she said: "This incident has had a profound effect on my life and a year on I relive the assault on a daily basis.
"If I'm out shopping at local shops where this took place I'm constantly on edge."
Then just over a month later Nelson struck again, this time with Jason Scanlon, now 28, at a property on Cook Close, South Shields.
The court heard two separate men were heading to the address but as one returned outside to visit his car, he saw the defendants, who demanded cash.
Ms Recorder Davies added: "Both of you were armed with knives and one is held to the throat of one complainant as he sat in his car."
One of the victims was able to escape Nelson and Scanlon, but the other had his phone stolen and despite the pair initially running off, they were later arrested.
Nelson, formally of Dock Street, South Shields, had just one previous conviction but pleaded guilty to affray, unlawful wounding, robbery and possession of a bladed article.
Scanlon, formally of Cook Close, has 32 convictions for 60 offences and also admitted affray and having a bladed article.
Meanwhile Calvert, of Horton Avenue, South Shields, pleaded guilty to affray.
Steven Reid, defending Nelson told the court his client's behaviour was linked to his immaturity and "thoughtless behaviour", but during his time in custody has been able to address his substance mis-use.
Gavin Doig, for Calvert, said his client had shown remorse at his actions and was capable of being rehabilitated.
The judge sentenced Nelson to three-and-a-half years imprisonment before also jailing Scanlon, who has been in custody since last January, to 21 months.
Calvert, was given 12 months suspended for 18 months with 30 rehabilitation days and 150 hours of unpaid work.