Aminu Adamu Mohammed was released on Friday after authorities dropped the charges on ''compassionate grounds.".

Mr Mohammed denied spreading ''false'' information during a court appearance.

He denied defaming Aisha Buhari in a tweet suggesting she had misused public money to her satisfaction.

But in a series of tweets and video messages over the weekend, the 24-year-old undergraduate apologised to Mrs Buhari for the initial tweet.

''It was never my intention to hurt your feelings'' he said, promising to ''change for the better.''

Mr Mohammed also thanked Mrs Buhari for forgiving him, describing her as ''our mother.''

He described his experience as ''the darkest hours of my life.''

He did not give details but he expressed his ''heartfelt gratitude'' to those who showed him support saying his case should serve as a ''lesson to all of us".

His apology to Mrs Buhari has sparked controversy on social media in Nigeria with many users saying the first lady should apologize to him instead because of the way he was treated.

But there are some who say his apology was right in order to resolve the dispute.

The arrest and the subsequent charge against the student had sparked outrage in Nigeria with many social media users and rights campaigners calling for his immediate release.

On Thursday, Amnesty International said Mr Mohammed was subjected to "torture" and other forms of "ill-treatment" after his arrest, calling it a "deeply repressive act" that "brazenly violates his human rights". Nigerian authorities have not yet commented on these allegations.

Mr Mohammed is studying environmental management at the Federal University in Dutse, in the northern state of Jigawa, and is due to start his final exams on Monday.

Nigerian President Muhammadu Buhari and his wife Aisha Buhari, during his inauguration in Abuja, Nigeria 29 May 2015