Try not to be scared - definitely have it check out... But hopefully it's just a zit - it could even be a node but an upset one. Your body's been through a lot chances are you're still glowing in the dark. Because of the radiation and all that's been done to you hour nodes may be inflamed etc... Or you may have a bit of an infection - it may even be a clip or a stitch or an air pocket. Not sure if you know what they do to you during a neck dissection but I apparently have a few clips inside my neck.. Ala Frankenstein style... One is actually in my scar line and you can see it through the scar it's so superficial. Here was also an air bubble on my collar bone - tine - maybe 2mm - that went away- it was a hold over from my surgery. They don't only cut where your scar is - they pull the skin away from your face and cut in to your internal throat. So there are all sorts of fun things in there after their done. Hugs again try not to worry. But do have it check out - even if it's just for peace of mind