The victim, a 59-year-old woman also from Bosnia, was taken to hospital suffering from stomach pains and had to be operated to remove a piece of shrapnel, according to a report from the SDA news agency.
The woman had alerted police to the attack about an hour after it happened, although she attempted to minimize the incident and initially complained of just a finger injury.
Investigators discovered parts of the grenade in the street.
An analysis showed that the armament was hand-made in the former Yugoslavia, police said.
Its detonation blew out a window in a nearby house.
The man suspected of throwing the device was caught on Sunday at the Italian border in Chiasso, in the canton of Ticino, after he returned from a brief visit to his home country.
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It is not clear what the motive for the hand grenade attack was.
An investigation into the case continues.