First we have to assume that all of the hydrofluoric acid is reacting (which is a reasonable assumption). From the stiochemistry of the reaction you know that one moles of hydrofluoric acid acid reacts to give a mole sodium fluoride and a mole of H+ ions.
so the ph should just be
but then i havent accounted for the affect of the following eqaulbirum
in which case you would need to know the water dissociation constant for the given conditions.