Ismail Musa, 26, approached Christel Stainfield-Bruce as she was walking home from work in Islington, north London, with her three-year-old son asleep in his pram.
The incident happened on 7 June.
Ms Stainfield-Bruce, 36, told Sky News that the man – who she believed at the time to be a teenager – came up behind her to ask for directions to the Emirates Stadium.
She said: “I stopped to gesture in the right direction, looked at him [he was] just a young boy.
“I didn’t necessarily feel any fear at that moment and then he said, ‘Give me your phone’ and I said no and then he just reached around to the back of my left thigh and stabbed me in the back of it – so so quick.”
The mother-of-three said the attack “didn’t feel like a robbery” and thought it could have been a “gang initiation”.
“It felt to me like the goal was to stab me,” she said, explaining that he did not try very hard to “get any financial gain”.
Ms Stainfield-Bruce was taken to hospital in central London but did not have life-threatening or life-changing injuries.
She said doctors had told her the wound was “quite deep”, about three inches wide and “quite clean” so it was “obviously quite a sharp knife”.
Musa, who was sentenced at Blackfriars Crown Court, will be put on an extended licence period for three years once released from prison.
Knives found at his home will also be destroyed.
Lucy Akerele, from the CPS, said: “This was an unprovoked and brazen attack on a young mother who was walking home with her three-year-old son in the middle of the day.
“Musa attacked the victim in daylight in front of passers-by and it was lucky that the young child, who was asleep, did not witness the violence directed at his mother.”