How do i deal with a flirty coworker?

Hi everyone, it seems i have run into a problem that every woman seems to go through after she gets a promotion...I have a guy in my team who can get flirty a lot Now, I know the obvious thing would be to tell him outright or to call HR, but i actually have a complex situation that ill explain So, i am a team leader, basically I head a team of 8 people in one of the leading banks of India, our job is to source housing loans for the bank Now, my husband doesnt live with me as he is in the army so i live with my in laws here, the last thing i want is to trouble him regarding this He was pretty normal initially although he did compliment my dress almost every other day, i think i probably should have stopped him there as it made him get more confident apparently Now he literally messages me at 1 am at night sometimes asking me for some papers and when i tell him that is not the professional time to message he just apologizes and then continues talking about some random office stuff at me AT THAT TIME ITSELF. I cant deal with this but he is like the second best performer in my team, so him going would be a hit to the team too What i am looking for here is that, is there any way i could easily make him change his ways? Or i could appear sterner to him in some way so he seizes his shenanigans I hope people with more experience than me managing teams can help me out here, thanks.