I recently had a xray with contrast that showed enlarged lymphnodes what could this be its in chest just below neck?

Many possible things. There are many things that can cause enlarged lymph nodes. It sounds like the area you are describing is the mediastinum? Infections can cause this, benign diseases such as sarcoid, and different types of cancers. What to do depends on your age, health, size and location of lymph nodes. Often patients like you would be referred to pulmonologist, oncologist or perhaps managed by your internist.
Need more tests. You need a good exam, ct scans, and most likely biopsy of the lymph node. Could vary between some type of infection to a lymphoma or lung cancer. Your age and whether you smoke are important to the doctor.