Supraclavicular lymph node inflammation?

Hi I have a slightly complicated story,

I am a 27 year old caucasian male with no family history of cancer.

I underwent a PET/CT scan at the beginning of December for some inflamed lymph nodes in my occipital region and to investigate the possibility of Squamous Cell Carcinoma (long story involving a lot of people giving me a lot of different interpretations on a diagnosis) and it came back clear. FNA of the offending nodes also came back clear. MY full body PET scan highlighted nothing suspicious anywhere at all.

Recently I noticed my right supraclavicular lymph node was inflamed. I'm unsure when this happened, I just happened to be fumbling around the area and touched on it, it seems to be roughly a centimeter in diameter and firm yet highly mobile. I did a little reading around and found some scary statistics about that particular node, notably that in people over 40, this turns outs to be malignant 90% of the time and in people younger than 40 about 25%. Although I'm in the lower risk category 25% still scares me.

I went to see the doctor today and he gave me some anti-biotics and anti-histamine tabs to take for a week and then told me ti come back in a week.

My query is this: As my PET/CT scan was clean with no suspicious areas a month and a half ago, does that rule out cancer for this (at least for lung cancer, to which I believe this node is mostly related)? I asked about the possibility of Lymphoma to my doctor and he grunted a laugh and said "No .... well at least the possibility is very very small. Either way take the meds and come back again later".

Other things that may be pertinent: I have a rash, but this is not unusual as I am a life long eczema sufferer (the eczema on my scalp was blamed for the occipital lymph nodes being flared). I also have viral conjunctivitis and the lymph node in front of my right ear is swollen as a result). In terms of possible virus contact, my wife recently had influenza but I didn't seem to contract it from her.

If anyone has any insight into what this could be I would be most grateful, ofc I will continue going to my practitioner, it seems there are very few alternatives on the web to "cancer" for inflammation of that particular node group, so I am a little worried.  

Many thanks

G