Have a small soft lump on my neck after day 2 of zpack -- dr. originally put me on it since he detected slightly over sized lymph node on left side?

Could be: just a lymph node, but obviously hard to say without examining you. Also more information would seem to help out, as did your doctor just start you on a Z-pack because a suspected enlarged lymph node alone or where you having other symptoms, like a sore throat, cough, tooth pain? Remember there are many causes to enlarged lymph nodes, many non-bacterial, that won't respond to a Zpack.