I was thinking a swollen Lymph node. You can have these for a variety of reasons (such as a blocked lymph node or infection elsewhere in the body) I have had one for years but fortunately its not painful. No cause can be found for me just popped up one day and has never left.
Could be a goiter but goiters tend to be central to the neck more so then to one side. Hope you and DH finds out what it is and have some treatment for the pain.