Un asunto de poca monta los tenía alborotados.

Un asunto de poca monta los tenía alborotados.
 

CAn anybody correct this sentence for me ?
An unimportant matter had everybody disturbed. Do you know of any closest ?

Your translation is fine.
De poca monta = of little value/of little importance/unimportant

A little more colloquial equivalent would be:
A (minor problem/small snag/glitch) had everybody up in arms.
They fussed over nothing.