If you want to file taxes as MFJ, your husband must have either an SSN or ITIN. No exception. His Nigerian number is irrelevant. If your tax guy is really good, he should know how to apply for ITIN for your husband.
Without SSN or ITIN for your husband, you could have filed MFS instead. Then amend your filing to MFJ after he moves to the US with his immigrant visa and gets his SSN.
