Prasetyo said the man who attacked the security official during a visit in Banten province may have been exposed to the Islamic State group.
"He is now being treated and undergoing surgery", Widodo said after visiting Wiranto, a former armed forces chief.
The attack came just over a week before Widodo's inauguration for his second five-year term in office.
Wiranto is a former military commander who is known as one of President Joko Widodo's closest aides.
Police have reportedly arrested a man and a woman, and are said to be investigating whether they were inspired by Daesh*.
Wiranto was later rushed by helicopter to the capital Jakarta. Videos showed him being carried on a stretcher, the left side of his abdomen covered with bandages and an oxygen mask strapped to his face.
Wiranto, who uses one name, was getting out of a vehicle in a town square in Banten province when he was attacked. Police had arrested a man and a woman they suspected were a couple, and seized sharp weapons they were carrying, including knives and a pair of scissors.
The government scrambled to tighten its security laws after a series of suicide bombings linked to the Islamic State-inspired Jemaah Ansharut Daulah (JAD) group killed more than 30 people in the city of Surabaya past year.
Investigations are underway to find out the groups that the two attackers belong to, he told local TV One.
He was blamed for the deaths of more than 1,000 people in East Timor when the province voted for independence in 1999, according to the BBC.
JAD has been blamed for past bomb attacks in Indonesia, including an attack on a church in 2018 that left 13 dead, the BBC reported.
He ran unsuccessfully for president and vice president in 2004 and 2009, respectively.