Hello!

I assume by leaving Germany and moving to Croatia, you have abandoned your asylum application (which had very low chances of approval anyway, unless you can prove that you were politically prosecuted in Nigeria). Thus you cannot return to Germany, because you have no basis to get a residence permit. Sorry!

Thanks for your reply,
But I think by married an Europe citizen that I have a right to live with her in any Europe country.

Oh, sorry, I didn't think of that - of course as spouse of an EU citizen you can move to Germany together with her. But only if you do not financially depend on the state - thus you cannot get social security (HartzIV) or similar, but need to earn your living expenses.
If you want to do that (and found a job that pays enough), you need to apply for a family reunion visa (Visum zur Familienzusammenführung) at your nearest German embassy before you move to Germany.

Ok..Thanks I will see what to do

Please, as a Nigeria that married a Croatian woman, I hope that I have a right to apply for a family reunion visa in the Germany embassy here in Croatia. Thanks

As I said, you do have that right, but she (or both of you together) have to show sufficient income to ensure survival without state aid (minimum €8700/year per person), accommodation (rental apartment or similar) and health insurance.
That's the requirement!