Buhari gave the indication on Friday in his remarks at the inauguration Gala Night held at the Banquet hall of the Presidential Villa.
He said that his administration would focus on agriculture and mining to engage the unemployed youths who form more than 60 per cent of the population.
"I ask Nigerians to please bear with us; a lot of damage has been done," he said.
He said that he had lost elections in the past three times and gone to the tribunal with the help of Nigerians, but that he was happy that the will of Nigerians made his victory possible this time around.
He said that Nigeria, being a populous country, if things went wrong in the country, they would go wrong in Africa because the continent could not manage any refugee crisis from Nigeria.
He said that when he consulted the foreign partners and confronted them with the refugee scenario, it pricked their consciences and they assisted with technology to enable a successful vote count in the last elections.
Buhari insisted that previous election results were written in private homes and announced on the radio and that getting the courts to reverse them was difficult.
He said that Nigeria’s friends in Europe and U.S. had spoken to him personally and had identified security as the major challenge facing the country.
"Nigeria has to be well secured and efficiently managed; this is what the APC is all about.
"This was why the legacy parties made the sacrifice of jettisoning their personal ambitions, tried to come together and took the bull by the horn and therefore brought it down and slaughtered it literally."
He said the party in power had realised its problems and made the sacrifice.
Buhari said: "Nigerians pray a lot; we need to even pray the more for luck so that expectations our people have, especially the youths would be met."
He said the unemployment level was the "keg of gunpowder we are sitting on" and the administration had resolved to secure Nigeria as soon as possible.
He thanked Nigeria’s neighbours for helping the country to fight insurgency.
He added that his administration would articulate the nation’s requirements after studying the handover notes from the past administration then consult the immediate neighbours, Europe and U.S. for possible assistance.
In his remark, former Vice President Atiku Abubakar described the inauguration of Buhari as historic for the nation and indeed Africa.
He said the transition from one party to another was a big achievement for the country.
"Democracy is the winner and Nigeria is the winner.
"I congratulate all those who made the election possible. I also congratulate former president Goodluck Jonathan for deepening democracy," he said.
He said the path of honour Jonathan took would not be forgotten and added that the new administration would need time to take stock and take decisions that would push the nation forward.
He urged the new president to recognise the diversity of the country and accommodate all since the nation’s diversity remained its strength.
APC chieftain, Sen. Bola Tinubu, said that a new era had dawned in Nigeria.
He said that a commitment to build a new Nigeria had been consecrated adding that "Buhari is principled, passionate and determined to develop the country."
He said the time was ripe for Nigeria to maintain its lead in Africa and the African renaissance must begin with the new President.
"The Challenge is yours. We that are looking up to you will continue to do so with great commitment and perseverance.
"Nigeria must lead," Tinubu added.