Socrates was, of course, being disingenuous, and ironic. He knew lots of things. He knew he was an Athenian, that he lived in Greece, that he was a male, and ever so much more. What he had in mind when he said he knew nothing needs interpretation.
Yeah, I get that much. The above post made use of my interpretation of Socrates' famous saying.
He probably meant that he knew nothing of importance, and that knowing he was a male wasn't an important piece of knowledge. He was probably talking of philosophical knowledge of some kind. He may also have meant that his knowledge was not absolutely certain knowledge. It is difficult to say. In the dialogue in which he expresses this, he is contrasting himself with others who claim to know things which he clearly thinks they do not know, and he interprets the Delphic Oracle who tells him that he is the wisest man in Greece as meaning that he is the only man in Athens who knows he knows nothing but that he knows nothing.
To know "nothing of importance", to speak of "philosophical knowledge", and to suggest that "his knowledge was not absolutely certain knowledge" are three items which are not necessarily mutually exclusive.