Hi, you're right that there really isn't a way for you to know the difference without experience. But you would know "rock hard" (calcified), which is what is usually talked about regarding metastasis in a node around the clavicle - and you don't have that.
The best thing to do is to continue to get educated in nodes so that you are prepared for the doc visit. You probably have 'reactive' nodes, especially if they came up suddenly. If they seem suspicious in any way, the doc might order a sonogram to rule out lymphoma.
If you have an Fx of immune problems, or if you have exposure to some pathogen, that should also help you to relax somewhat - i.e., it's not lymphoma.