I had asked for some further information and have not heard back.
If the pain is occurring diffusely, it is more likely to be either an infection or an inflammatory condition. If it is more localized, then it is more likely to be musculoskeletal.
When there is more diffuse muscle pain of recent onset, it is frequently due to a viral
infection, particularly if it is associated with a fever. It also could be a diffuse inflammatory condition.
If there is muscle weakness associated with the pain, it would be more likely to be a more serious muscular or neurologic condition.
The recommendation by your doctor is a common approach, as a short course of an NSAID will treat most of the common causes of muscle pain. In someone that should not take NSAIDs, the other common alternative would be to use acetaminophen. It does not relieve inflammation, but also does not irritate the stomach. If plain acetaminophen is not sufficient, then stronger medicines would only be available by prescription. It also would be reasonable to apply moist heat, and for diffuse muscle pain, it can be best accomplished by soaking in hot bath water or a hot tub.
If I can provide any further information, please let me know.