Hello and hope you are doing well.
The 'lump' could be a sebaceous cyst, a lipoma, a thyroid nodule or lymph nodes. They could also be herpes infections, cysts, yeast infections and infected hair follicles. If there is accompanying swelling, redness, discharge and fever it is most probably an infection. You may need to consult your primary care physician who will examine you and initiate appropriate therapy.
Hope this helped and do keep us posted.
I'm gathering it's on the outside of your neck?
If so it could just be a knot. It's when muscles develop a gas/air pocket.
In most cases applying pressure and rubbing in first a clockwise and then a counterclockwise motion will cause the gas/air to leave.
If it's inside, then I would suggest seeing a doctor. It may be a growth that needs to be removed.