I would check that out further to make sure it's not part of the crop you are feeling.
IF there is an Air Pocket under the skin, then if possible, consult and Avian Vet to see if they can release the air for you or some do release the air at home using a sterile needle.
If an Air Sac has ruptured, this can cause respiratory distress. There are 9 Air Sacs found in poultry. 2 are located on either side of the neck, 1 (the Interclavicular Air Sac) may be what you are feeling if it's above the Crop.
Videos below of how to release air is below. Pretty much standard regardless of where the rupture is located or age of bird.
