U/S thyrois normal, Lymph Node FNA positive, PET Scan negative

I have had a small lump in my neck (lymph node) for about 2 years.  No symptoms and blood work (CBC, thyroid function) normal. My PCP didnt find it suspicious and said to monitor it (at the time the lump was less than 1cm). Recently, I decided to get it checked again and my PCP referred me to an ENT who did an ultrasound.  He said thyroid looked normal and decided to biopsy the nodule (which is now 1cm). FNA came back positive for papillary cancer.  He sent me for a PET scan which came back negative.  I have an appt with my doctor this Friday and he mentioned he would do another biopsy.  I'm so confused. If the thyroid appears "normal" on U/S, can you still have thyroid cancer in a lymph node?  Also, should I request the I-131 scan?  I don't know what I should be doing or asking as this is all so new to me.  I am 34 yrs old and have no symptoms and blood tests are still normal.  I don't have any other nodules.  Thank you all for your time!