Hello and welcome to MedHelp. It's always worrying when we find something on our body that we don't think is right. Lymph nodes have a bad reputation and scare us. However, remember that lymph nodes also provide a function and can be an indication that they are doing their job for our body. The lymphatic system is part of our immune system. We can have a swollen or reactive lymph node for quite some time after our body has fought off an infection. So, your lymph node in your collarbone could be just that. If you have, were or are fighting off an infection of the throat, for example, that is a common place to have a swollen lymph node.
I would not assume cancer especially with the way you describe your lymph node. Has it been there consistently for more than two weeks? If it has, then please make an appointment to see your doctor and have it evaluated. Again, I would not assume cancer.
Here is an overview that is very helpful on lymph nodes. https://my.clevelandclinic.org/health/diseases/15219-swollen-lymph-nodes
Please let us know what you think of this information and when you make an appointment with your doctor. Best of health to you.