Sir, my mom suffering from pain in her neck on back side, what is the problem, let me know please , i m very thankful to you?

Many possibilities: There are many possible causes of pain in the back of the neck. A doctor can evaluate to figure it out. There could be a muscle strain or spasm, inflammation in the joints or tendons, nerve pain from the spine or on the skin, an outbreak of shingles, etc... If a person is older or otherwise at risk for cancers, the doctor will look for tumors as well. Young people more often have muscle strains.