pain in the arse
Not literally a pain in one's anus or gluteus maximus, though either would count.

Something quite annoying, but not as bad as a ballache, which would also be expected to last longer.

People, Places, Things: it doesn't matter. Often shortened to just: a pain.
Was that your uncle?

Yeah. What a pain in the arse.

Well, i wasn't gonna say anythin, but...

You wanna meet my Dad! What a ballache. Shit, he's coming over, time for a cool sharp one.