What Causes Sore Lump On Right Side Of Neck?

Hi there I have a lump on my right side of my neck , well when I say a lump you can t see it unless I put my arm up half way , it s like a muscle or something , it s sore , I went to my drs who sending me for an ultra sound , also part of my shoulder at back is inflamed, this is sore I ve had this about 5weeks now, I m worried sick, my sister had chondrosarcoma last year in her arm , my other sister has fibromyalgia , also my mum had that too, I m 45 years old and really worried please help thank you selina