lump on my collarbone

It was a year past Halloween that I had a lump in my neck biopsied, then subsequently being diagnosed with thyroid cancer and treated for this.  I now have a nut sized lump on my collarbone.  I have an appointment at the GP for this tomorrow - hoping it is just a cyst!  But I am worried in case this is something else.  Has anybody else experienced a lump on their collarbone after thyroid cancer?

Thanks x