The terms homogeneous and heterogeneous refer to mixtures. A mixture is a combination of two or more substances that have not undergone a chemical reaction. Pure nitrogen is not a mixture, therefore is neither homogeneous nor heterogeneous.
Nitrogen is a colorless, odorless and tasteless gas. It is an inert gas under standard temperature and pressure. Nitrogen is ranked as the seventh-most-abundant element in the universe.
Homogeneous mixtures have a uniform composition and the same properties throughout. Heterogeneous mixtures are not uniform, and have different properties throughout. Air is a homogeneous mixture of nitrogen, oxygen and small amounts of other gases.