This is an adjectival expression best used to describe people, places, things, moments, and events that are so annoying/stupid/ridiculous/grating that patience diminishes, moods deflate, and the threat of violence increases. Basically, this phrase can be used to describe anything or anyone that grates on your last nerve.
The fact that we are having a departmental meeting to discuss cover sheets and TPS reports really makes my ass hurt.
An obscure saying with suspected origins in Ireland. Used to express indifference or lack of concern about a particular choice or outcome. Synonymous with "makes no difference." Typically used in the context of expressing personal nonchalance.