Hello~It might be a muscle spasm, but I would keep a watch on it and if it starts to hurt or grows then definitely see your GP.
I noticed the same thing a few months ago & went to an Ear, Nose, & Throat specialist. He had me get a CT scan. Turned out to just a normal part of my bone structure, the Transverse Something or Other. Why it sticks out way more on my right side than the left, I don't know. But he assured me it's nothing to worry about. It wouldn't be a bad idea for you to get it checked out by dr. if you haven't already. There are lymph nodes in that area that can swell due to either infection or cancer. Cancer is unlikely but it's best to get it checked.
I think this sounds a bit like a lymph node that is reacting. I had this when I had a tooth issue. Is it gone now?