Suggest treatment for discomfort and pain on the neck
Ultrasound abdomen and guided biopsy is must in your case.
I understand your concern.
This definitely isnt GERD.
Only two major possibilities should strike the diagnosis in your case.
1.Inflammation of thyroid-thyroiditis or any thyroid pathology
2.Swollen lymph node in the pre and paratracheal region.The cause of which is once again thyroid pathology or other source in the oropharyngeal cavity.
For differentiating both I advise you to have an ultrasound of the neck and U/S guided FNAC of the plopping mass.
Further management depends only the outcome of the test results.
Post your further queries if any.