A colleague of mine who's also my subordinate has sent me inappropriate emojis (kissing and the likes) few times. How do I put him in his place?

He's married, has a kid. Neither have I indulged in any sort of discussion with him other than work nor has he brought any topic up during our conversation. He sent the emojis over WhatsApp while complimenting my profile picture. I thought I was overreacting. Should I tell him anything?