HNO₂ acts both as reductant and oxidant, while HNO₃ acts only as oxidant. It is due to their:

In $\stackrel{*}{{\mathrm{HNO}}_2}$ oxidation number of N = +3, HNO₂ oxidized to +5 and reduced to +1so it acts as Oxidant and Reductant
In $\stackrel{*}{{\mathrm{HNO}}_3}$ oxidation number of N = +5 ,HNO₃ acts as only Oxidant due to it is reduced to +3.