First, both parties must be legally capable of entering into a marriage. This means that they must be of legal age, of sound mind, and not already married to someone else.
Second, the marriage must be performed in accordance with the laws of Nigeria. This includes obtaining a valid marriage license, having the ceremony performed by a legally authorized officiant, and having two witnesses present.
Once these requirements have been met, the marriage will be considered valid in both Nigeria and the United States. However, it is important to note that the U.S. government may require additional documentation or procedures in order to recognize the marriage for immigration or other purposes.
For more information on the legal requirements for marrying a Nigerian citizen in Nigeria, it is best to consult with an immigration attorney or the U.S. embassy in Nigeria.