If your child has a lump on its neck and you can move it around, it could be a couple of different things. It would be best to take him to the doctor so that the doctor can tell you what it is for sure. It could be an infection.
it could be lymphoma, a skin boil, swollen lymph node, a thyroid problem, thyroid cancer, or goiter. dont think the worse case scenario just dont come asking 'ask.com' when a doctor is the one with the degree