What message should I read this gesture?

What does it mean when your doctor comes up to you at the waiting reception with a whole lot of other patients waiting to see the doctors on duty and gives you a quick poke with his finger?

The doctor walks out of his consultation room and chats with someone at the reception counter. Notices me and I try to avoid his gaze and pretend to look for something in my bag and then he walks towards me and I feel this finger poke on my arm, near my wrist. I am startled, looks up and say, Hi and how you’re doing. He then smiles and nods and walks back to his room.

What is the message being conveyed with this gesture? Should I be assuming anything more than just a simple way of saying hello?