i would advise you not to indulge in any form of 'popping' of the spine as it has delicate spinal cord
and nerves around that area which may get damaged.
if there is pain in the back near the spine it could be related to vertebral
column or muscles in the region.
did your partner take any pain killer for the same? if the pain killer is not relieving him of pain and if it is more than 2-3 days then you should see a orthopedics doctor who would advise you to take an Xray to rule out any bone problems and suggest treatment accordingly.
if the pain is more you can try to take hot fomentation to the are it will soothe if it is muscular.