How likely is this a tumor

Hey all, I (f21) have this hard lump on my neck. It's very firm and doesn't really move around, I initially thought it was a swollen lymph node but it's been like this for about 2 months. My concern is i already have a brain tumor, and don't know ow if I'm more likely to get more because of that. I have a doctors appointment tomorrow but how worried do I need to be? I'm so scared.