Lump on left side of collar bone causes?

Nonspecific: Unfortunately this is an extremely nonspecific description. A soft fatty lump may be a simple lipoma, which is benign and does not require treatment. If you have had prior fracture of the collar bone, you may be feeling a bony callus or a residual deformity from the fracture. If the lump is tender or has unusual coloration or has been rapidly changing in size, then you need evaluation.