We don't have a direct translation. You'd just say something like "I've been working hard," or "Thank you for the hard work."

"辛苦了" is to express how much we appreciate someone's effort. Appreciate it! I appreciate all your troubles. We appreciate your effort. I appreciate all your hard work.

In Chinese, as I know, people also say to someone who just arrived, for example in the airport-辛苦了吧？ That means "You should be tired?" . "working hard" is also one of the meaning.