Hi,I Have A Hickey Like Mark On My Right Arm..

Hi,I have a hickey like mark on my right arm.. it just appeared last night when I was working. For work I lift bundles of papers and constantly use my right arm but I've been doing that for over a year now and this is the first time this mark has appeared so I'm not sure if it could be work related or not.
The marks on the inside of my arm just under where my elbow bends