I had one in my twenties on my neck. Pretty big. No illness etc. Dr checked me over thoroughly. Bloods came back showing I was fighting an infection of some sort but nothing that was bad enough to actually make me feel ill. Dr said sometimes your body is fighting infections/viruses that you don't know you have. So it was nothing. But the node has been slightly large ever since ( which is normal). But yes always best to get these things checked.
DD had one- reoccurred recently. Turned out that she was just fighting an infection and the HPV vaccine triggered it once too. I know what you're thinking! I did too. It would be silly to say don't worry, because it's normal to worry, so just go and get checked out tomorrow. Blood tests will put your mind at rest, as they did ours.