More polite way of saying "don't disturb me" [closed]
How can I say "don't disturb me" in more polite way when I am busy
This question might be slightly better suited for the Interpersonal Skills site (https://interpersonal.stackexchange.com/questions/tagged/etiquette).
That said, you could try something like "I'm sorry I can't chat right now, I have something I need to focus on. I can get back to you after I'm done." Of course, this is assuming you actually will follow up with the person who interrupted your task!