I want to relocate overseas from Nigeria before the end of the year, i don't know between Europe and America which is of a better option, I am 45, a graduate of Business management with technical and IT skills. I need advice from experienced people and also Nigerians overseas.
I would also like to know if it is the right decision for me to make now because I currently earns about N250k monthly from my business here in Nigeria.

Try the States.

Canada

Canada

Uzbekistan

Canada
US
A black nation in the Caribbean
UK
New Zealand
Australia
A Scandinavian country
Spain

Also, Senegal, Ivory Coast, Kenya, South Africa, and a few other places could be good options nearby (not certain, do your research). I would say Ghana, but they seem to be being nasty to Nigerians lately. It's a shame.

Thielngr:
I want to relocate overseas from Nigeria before the end of the year, i don't know between Europe and America which is of a better option, I am 45, a graduate of Business management with technical and IT skills. I need advice from experienced people and also Nigerians overseas.
I would also like to know if it is the right decision for me to make now because I currently earns about N250k monthly from my business here in Nigeria.

It depends on your choice but however, you can try Canada or Aussie. They're cool but age is a big factor too tho.

For Canada and Aussie, your age will affect you if you using the skills migration route. The maximum age for Aussie is 45yrs which you've already clocked. Except you have a wife whose age is below 45 to serve as primary applicant.