enlarged lymph nodes subsequent to melanoma

I'm a 52 year old male, in generally good health. In July of 2005, I had a Stage 1A (.55 thickness,level 3)melanoma removed on my upper right neck, just below the hairline. I was told that it was caught at a "low risk" stage, with a probable survival rate of 95%-98%. I, of course, go in for regular checkups now. I saw my dermatologist in January for a full body check, including palpitation of lymph nodes in the neck, armpits etc.....he did not detect anything unusual. From about mid Jan. thru March, I seemed to have one long, drawn out cold. Finally went to my internist, was diagnosed with an upper respiratory infection, swelling of the eardrums, and also had significant enlargement of the lymph nodes on both sides of my neck (low, and just in front of the mid-line) I was prescribed a ten day course of antibiotics and given a steroid shot, and told to go see my dermatologist again if the swollen lymph nodes "persisted" more than two weeks. Most of them reduced in size....on the right side, one is still barely palpable, but on the left side(opposite the side where the melanoma was located), I would say that the node has not really changed...it is still about the size of a pea, movable,slightly oblong in shape and somewhat rubbery in consistency....not really painful at all now (except for a general soreness there because I'm always feeling it) My dermatologist said he believes the chance that it is recurrent melanoma is "remote", gave a preliminary diagnosis of "resolving viral infection", and wanted me to come back in a month if it stayed enlarged....its been two weeks, with no discernible change, and of course, now I'm getting concerned, to the point this is clouding my entire life.... Obviously, from what I've read, this could be several different types of cancer, including metastatic melanoma, but I've also read that after a bout with a viral or bacterial infection,lymph nodes can remain enlarged for a very long time, even permanently. Obviously, I'm going to listen to what my doctor recommends, but how is a determination made that a biopsy is necessary in a case like this, whereas a person who had not had cancer before may just "wait and see"? This has been going on for 3 months....am I just being neurotic? I sleep well, not losing weight, no night sweats....basically in pretty good health otherwise....