Why did a steroid shot not help my lymph node swelling? are there other causes besides possibly cancer that would keep the lymph nodes enlarged after steroids?

I would not expect a steroid shot to reduce lymph node swelling. The swelling is a natural process when the node is called on to work by processing/filtering lymph of debris. The debris can be from localized bug bites/ inflammatory chemicals/infection. Swelling goes down after the work is done, usually over a period of several weeks. Rarely the swelling must be drained. Cancer is low on the list.