Will sodium sulfite effect the oxidization of toluene to benzoic acid with potassium permanganate?
How do you know your permanganate contains sodium sulphite?

It seems highly unlikely because $\ce{KMnO4}$ is a very strong oxidiser and sulphite is very easily oxidised to sulphate:

$$\ce{SO3^{2-}\to SO4^{2-} +2e-}$$

Also, it seems improbable to find a sodium salt in a potassium salt.

Even if the $\ce{KMnO4}$ contained some "surviving" $\ce{Na2SO3}$, during the oxidation of the toluene, it would quickly be oxidised to sulphate. At worst your benzoic acid yield would suffer slightly.