HI There, I Splattered Some Oil On My Neck Today

HI there, I splattered some oil on my neck today and when looking closely saw that I have a swelling on the right side of my neck just above the collarbone. I am doing a show at the moment (actress) and looked at the publicity photos today and saw that I have had this for at least four months! Just didn't notice. It does not hurt but is actually really rather large, it's about 5 cm long and starts at the hollow of my throat and goes up the neck at an angle towards my right ear? Any thoughts? Cheers, Rachel NZ