Nerve pain due to Vitamin B12 deficiency.

Patient: Hey doc, im 20 years old male 70 kg 6’1. Ive been taking nexium for acid reflux for the past 2 years on and off,and for the past week i started getting nerve pain in my hands and legs. Got tested for vitamin b12 deficiency and turns out I have a count of 105 which is very low. The doctor recommended I take b12 1000mcg everyday for 3 months. My question is, is this serious and what should I do?

Symptoms: Shocking nerve pain in arms and legs.