Thanks for writing to us.
The large lump on the collar bone could be due to a fracture
of the collar bone which might have remained undetected. The X-ray of the region will help in detecting the exact cause. Benign bone lumps also need to be ruled out.
I hope this information has been both informative and helpful for you. You can consult me again directly through my profile URL http://bit.ly/Dr-Praveen-Tayal
Dr. Praveen Tayal