Hi
From what I see here, It looks like you do not have any ties in Nigeria.
So the officer is not convinced that you would go back home after your studies.
I would suggest that when you re-apply, you should mention that you will be returning to Nigeria after you studies to start a non-for -profit organization or you have a potential job at your dad's law firm or something tangible to look forward to after school.
secondly, I would suggest that you apply to a school in Nigeria (maybe yabatech, or polytech) (for a short period of time). This is considered a tie because you have nothing else, you have no kid, you have no wife, you have no business.