Police detained 21-year-old Lokman Aslan after finding three dismembered fingers outside the police station in the city's Beyoglu district late on Tuesday, the Anatolia news agency reported. There were no other injuries.
Officers searching hospitals found Aslan four hours after the explosion at a private hospital, a few kilometres away. He also suffered neck injuries, Anatolia said.
On Wednesday, police detonated a homemade time-bomb in a courthouse parking lot in the city's Zeytinburnu district, Anatolia reported. The bomb had been placed under a car.
On Tuesday, Istanbul Governor Muammar Guler said police had detained 18 people in connection with the bombing of a Masonic Lodge on 9 March, including three who allegedly planned new attacks.
It was not clear if either bombs were linked to the lodge attack, which killed two people, including one of the attackers, and injured six others, including the second attacker.
The London-based Arabic newspaper Al-Quds al-Arabi said last week that it had received a statement from an al-Qaida-linked group - Jund al-Quds, or Soldiers of Jerusalem - claiming responsibility for the bombing.
One suspect charged with
Istanbul truck bombings
But authorities say the attack bore little resemblance to the four carefully planned truck bombings last November.
Also on Wednesday, a state security court, charged one suspected Islamist with involvement in the truck bombings in Istanbul last year, Anatolia said.
Ahmet Dikiciasik, 46, was detained at Istanbul airport as he tried to leave for Pakistan, the agency said. There was no information on when he was detained.
The court charged Dikiciasik with belonging to an illegal organization, which carries a prison sentence of up to five years, Anatolia said.
A Turkish court will begin trying 69 alleged al-Qaida suspects for the truck bombings on 31 May. Fifty defendants are in jail and 19 others have been released pending the trial.
Nine others, including three suspected ringleaders, are fugitives and could be tried in absentia although formal charges have not been filed yet.
Two synagogues were attacked on 15 November during Sabbath services, and five days later, bombings hit a British bank and the British consulate, killing 62 people.