Sodium potassium pump pushes 3 $N{a}^{+}$ out of the nerve for 2 $K^{+}$ that it pushes inside the nerve. This helps in maintaining the resting membrane potential. If it is blocked $N{a}^{+}$ won't be able to leave the nerve and will get accumulated within the nerve and $K^{+}$ will not be able to enter the nerve and will accumulate outside the nerve.