Oh, and have you been around any cats?
Hi, "Username". Just so you don't feel too worried, I'd like to point out the following to you:
Of all the people who go to see a doctor because of an unexplained bump on their neck, only a very small number end up having cancer. Maybe around 3%.
If it hasn't been getting larger, that's in your favor. Since you say that it is immovable, I'm guessing that you've done some research. Be aware that a lymph node being immovable doesn't necessarily mean cancer. We don't even know at the moment if it is a lymph node.
So, you can look at a visit to a doctor as the chance to rule out cancer.
Btw, is it round or oval? What's your age?
This could be a number of different things, but since you've had it for at least a few months, if not a lot longer, it's time to see your doctor.
I can't stress this enough. A lump on your neck can indicate a few different types of cancer. Obviously, I don't know if you have cancer, but you really should see your doctor to find out.
https://medlineplus.gov/ency/article/003098.htm