Poland did not have a Nazi leader. The Germans incorporated parts of Poland into Germany and Russia (which was their ally at that time), and the rest of Poland has been called "General government". The Nazi occupation forces were governed by a German called Hans Frank.
Please see the related question and the links from there. The extermination camps were in Nazi occupied Poland. Many of the ordinary concentration camps were in Germany, but there were also some in Poland.
The nazi regime in Germany began in 1933 and the World War II (by German attack on Poland) began in 1939, so it was impossible Warsaw was under nazi rule in 1931. Warsaw was under nazi rule from September 1939 to January 1945.