I’m a dual citizen of Nigeria and America. I also have a Nigerian passport, do I still need a visa to travel to Ghana?

I’m no expert, but I’d say no, you do not. I think what your friend was trying to say (from your comment beneath your question) is that if you have a passport from an ECOWAS country, you can typically travel to any other ECOWAS country without a visa. Nigeria and Ghana are members of the ECOWAS, but please look further into this.

Oh someone told me u can travel within Africa if u have an African country passport

Yes you do..

Call the embassy