HI,
I HAVE GONE THROUGH YOUR QUESTION. I AM A PRACTISING ANAESTHESIOLOGIST AND PAIN CONSULTANT.
IF I WERE YOUR TREATING DOCTOR IN THIS CASE,I WOULD COME UP WITH FOLLOWING POSSIBILITIES
1) CERVICAL SPONDYLOSIS - SLIP DISC IN NECK REGION
2) SHOULDER BURSISTIS - INFLAMMATION NEAR SHOLDER JOINT
3) NERVE ENTRAPMENT NEAR SHOULDER JOINT
4) FROZEN SHOULDER
AS YOU HAVE MENTIONED, IT CAN BE BECAUSE OF BONY SPUR ALSO
YOU SHOULD NOT WORRY TO MUCH.
I WOULD SUGGEST CONSULT A ORTHOPEDIC SURGEON AND YOU SHOULD GET MRI CERVICAL SPINE AND MRI SHOULDER DONE, ALSO CHECK FOR BLOOD SUGAR LEVELS TO RULE OUT DIABETIS
IF MRI CONFIRMS THE DIAGNOSIS WE CAN THINK OF SURGICAL OR NON-SURGICAL MANAGEMENT FOR YOUR PAIN

Dear friend, I have gone through your question...
Bone spurs can cause pain in shoulder and arm as it compress the nerve roots emerging from cervical(neck)part of spinal cord..The pain you are experiencing is nerve root injury pain or radiculopathy.
It would have been helpful if you mentioned the type of pain, whether any associated pins and needles sensation, loss of sensation to temperature in any particular area of upperarm, any associated weakness in any particular movements in shoulder.
You have to undergo a CT scan as a primary screening modality to assess the cervical spine.
If required (after primary screening), MRI scan can be done after consulting a physician.
Soft cervical collars can be modestly helpful by limiting spontaneous and reflex neck movements that exacerbate pain.
As advised by consultant NSAIDs, acetaminophen or both with or without muscle relaxants can also be used.
Bone spurs are one of the most common causes for pain in shoulder and arm.
Cancer is rarely a possibility.
Thank you.