Complicated question:
Naxopren is a NSAID and yes, like all drugs it MAY have side effects, short term or long term as almost all drugs do.
Do you want to suffer in pain against the chance of side effects from NSAID?
Arthritis does affect the joints, but the muscle pain is spasm in an attempt to protect the damaged joint.
The arm pain is almost certainly muscular in origin secondary to your cervical spine degeneration.
There will be plenty of posts following this on the benefits of "natural supplements" and I will leave it to them.