Pocket Of Fluid Developed On Base Of Neck. What Could It Possibly Be?

I have a pocket of fluid (it feels like fluid--not hard) that has developed on the left side of my neck at the base of my neck near collar bone between shoulder and neck. It is clearly NOT normal. My primary care , whom I am no longer going to said he thought it was fat....that s bull....I am a smoker so no respect there! If I broke my finger it would be because I smoke. I am not stupid, I know smoking causes cancer and all sorts of things...maybe even this. My question is, who do I see about this and what could it possibly be. I fell about a month ago and saw doctor, think I have injured my rotator cuff on this side but became very ill with virus directly after and never got to orthopedic ...no broken bones. What could this be? Will it go away on its own? My daughter looked at it last night and freaked out as she said mom, something is definitely not normal....get to a doctor . Any help would be appreciated.