Having gained more votes in the election, the Independent National Electoral Commission (INEC), announced Buhari as the winner of the presidential poll.
The All Progressives Congress (APC) candidate polled 15,191,847 votes to defeat his closest opponent of the Peoples Democratic Party (PDP) who got 11,262,978 votes.
The PDP candidate, Atiku, rejected the outcome of the election describing it as the worst election in Nigeria's history. He vowed to challenge the result in court.
Reacting to Atiku's decision, Mustapha said there is nothing to worry about.
He said, " We are not jittery at all because the process was open and transparent. It was a credible election and we will continue to savour the victory. In the process too, we will extend the hand of friendship for the purpose of nation-building and reconciliation."
Mustapha added that he will encourage "them to seek redress in court" since the constitution has given whoever is dissatisfied a window to do so.