Lump on left clavicle bone near my throat not sore and why is this ?

Hard to say: Hard to say. The clavicle articulates with the sternum medially. Sometimes the sternoclvicular joint can beome quite enlarged, often from an injury or an arthritic condition. This might be what you are describing. An exam and possibly an xray can usually determine the cause. Thank you for your question.

Simple vs serious: Our bodies always have things that grow and change. Skin, fat, muscle, lymph nodes, bones, can change shape, get larger, more prominent due to many factors. The vast majority are not cancer but simply unusual growths like fatty tumors, cysts, skin tags, moles, etc. Most cause no symptoms and can be watched. If they cause symptoms or change colors, bleed, bruise or hurt, then see your doctor.