The reason stated in the final decision letters states “
I am not satisfied that you will leave Canada at the end of your stay as a temporary resident, as stipulated in paragraph 179(b) of the IRPR, based on the purpose of your visit.
I am not satisfied that you will leave Canada at the end of your stay as a temporary resident, as stipulated in paragraph 179(b) of the IRPR, based on your family ties in Canada and in your country of residence.”
What amendments can I make agains reapplying for the study permit
Sorry to hear about your refusal. I know it must be frustrating after having invested so much time and money.
You may shift this query from discussions under 'Expression of Interest' to 'International Students' since you will get responses from applicants similar to you. This section is for candidates applying for permanent residence.
The refusal could be for any reason such as travel history (Have you travelled to countries such as the US, Australia, UK and returned to Nigeria before?) and / or ties to your home country (Do you have a stable job that pays well in Nigeria? Do you have family back in Nigeria? Do you have assets such as property or investments there? Is your selected course a natural progression in your career and related to your work experience or previous education?). Basically, the Visa Officer needs to be convinced that you have a bonafide student and have compelling reasons to return to Nigeria after your studies.
All the points listed above are discussed under 'International students' in various threads. Just search for them and I am certain you will find more information that will help you going forward.
Remember, do not give up hope as I've seen applications get accepted at even the third or fourth tries!
Best luck.