Hi, I was residing in the UK last year when I began this process and got my UK police certificate in September when I entered the pool, and left the UK for my home country Nigeria in March, now I got ITA yesterday, will like to know if my Police certificate from last year September is still valid for Express entry? Or since I left the UK in March, whether to apply for another one?
You will have to apply for another one. The one you currently have is no longer valid because you got it before you left the UK. That is, while you where in the UK.