Yes,lump at collar bone could be the cause
Thanks for posting
The collar bone, scapula
(arm bone), they together form the shoulder joint. Hence any disease affecting the involved bone may lead to pain and restriction of shoulder movement.
The lump could be because of Inflammation at junction of clavicle
and sternum? It requires physical examination of shoulder to confirm the cause.
My advice would be -
1. Ice fomentation along with Ibuprofen
to reduce pain and swelling with rest to shoulder movement.
2. Xray of the affected area and send the picture of lump in your reply if possible.
Looking forward to your reply.