$$2NO_2^- + 4H^+ + 2e^- \rightarrow N_2O + 2H_2O$$

In this reaction, NO2- undergoes reduction from a +3 oxidation state to a +1 oxidation state in N2O.

As an oxidizing agent:

$$NO_2 + e^- \rightarrow NO_2^-$$

In this reaction, NO2 undergoes oxidation from a +4 oxidation state to a +3 oxidation state in NO2-.