a lymph node will go away with time, it could be as little as two weeks, could be longer, it could stay enlarged for an extended period of time.. the doctor will be looking to see if it continues to get any bigger or harder.
A cyst will generally never go away, even if drained it is likely to fill again. A tell tale characteristic of a cyst is discharge, I don't suggest this, but squeezing a cyst usually will cause it to expell discharge.
Coincidentally.. I've had both a swollen lymph node AND a cyst on my neck.. at different times though. The cyst is like a zit.. that is what I thought it was until it didn't go away after over a year, plus it was white because of the puss building up inside it.