1. something difficult or unpleasant appears or becomes visible
Professional
Social
let's hope that problem doesn't rear/raise its ugly head again
Something which 'rears or raises it's ugly head' becomes visible or causes trouble especially after lying hidden for a time or having previously gone away. It can also refer to unpleasant topics being brought up by someone who is in a position of superiority. Usually, this phrase is used to talk about intangible objects.