I can understand your concern.
since you are asking this question for your wife, you have to enter your wife's details like her age, her height, weight and if she is taking any medications. not yours.
since when is she having this?
kindly consult a M.D. Consultant physician in person and get her examined. also she will need certain tests.
as of now you can take a pain killer and a muscle relaxant like tab. Zerodol -MR twice a day after food.
Dr. Anil kumar jain.
You must visit a general physician to personally assess & advise any investigations if needed. It does not seems to be serious. Could be due to 1. Muscular spasm 2. Related to spine or 3. Related to stomach & gas.