The German word "tja" can mean:
- oh well
- ho-hum
- too bad, tough luck
- What can I say?
- I told you but you didn't listen - now here you are, you sorry little f*ck
There's also "tja, nun" (nun = now) which is a more talkative version of "tja".
So, "tja" is a signal for some smart-ass "told you so" bad news coming your way.
And it's a great shortcut when you think you already made your point.
PS: None of this has anything to do with cha-cha-cha.
Enjoy our language!