Pain over right shoulder, in joint and spreading up neck and across clavicle? what is it?

Spasm: Sounds like a spasm of the trapezius muscle. If there was no injury and it came on quickly or you woke up with it, likely a spasm. You can try swimming if you have access to pool. If it doesn't resolve or gets worse, should be seen by doctor.

Spasm: Is the most likely problem stretching and hot/cold packs can be helpful, in addition to the the gentle exercise already mentioned.