What covalent bonds is the most polar hydrogen and fluorine or hydrogen and nitrogen?

Electronegativity Difference

HF = 1.9 = ionic bond

HC = 0.4 = nonpolar covalent

HH = 0 = nonpolar covalent

HN = 0.9 = polar covalent

HN is the more polar bond. HF is not polar covalent, it is ionic.