Can I Use com.ng for a big business?
For example we are creating a mini website that's is meant for all countries and the name we come up with does not have (com, or Co, or net, or org) it's only has com.ng and I m asking if it mean anything

Yes. It could localize your concept, and give out your origin too quickly.
.ng domains usually suggests localized business concepts.
I would advice you to do more domain search or modify your domain so as to get .com extension or of you can, buy the registered domain from the current owner