knife crime
Two men in their twenties have also been arrested.
He was one of three men in their twenties to be stabbed to death in 24 hours in London.
Fahim Hersi was knifed as he went to watch British action film The Intent 2 with friends.
Nottinghamshire Police say injuries are not believed to be life-threatening as cordon set up inside cinema.
By removing the film, Vue and Showcase are implicitly linking all black boys and black communities with crime, journalist Nikki Onafuye writes.
All of the victims were in their twenties.
Two people have been arrested.
The attack in Greater Manchester came weeks after a 61-year-old was stabbed nearby.
The teenager and her mother were both attacked during the "terrifying ordeal".
An 18-year-old man was stabbed to death in West London on Thursday.