The police informed about the incident, which happened in the area between Storgata and Oslo S, at 7.40 on Sunday morning.
The injured man is said to have taken himself to Oslo S, where he was notified by security guards. He was then taken to Ullevål hospital.
– It is described as stab wounds, but the extent of the damage is unknown. However, there should be no question of danger to life, says assignment manager Eirik Sandnes in the Oslo police district to NTB.
Sandnes says that it has not been clarified whether the two involved know each other or whether it was a random collision. The man was arrested in Torggata, not far from the scene.
– He is currently in custody. We will secure questioning of witnesses before he is questioned, says Sandnes.