Quick background: I'm relatively new at my workplace (a few months in). I was recently chatting with a coworker when I found out that I may be asked to present something to the team later this month. My initial reaction was one of slight anxiety and I expressed that to my coworker, who basically laughed at me. Once I had conquered the initial anxiety, he joked that he would remind me of the inevitable presentation so that I "don't forget it".
I've since gotten over my anxiety but he's sticking to his word and every day has sent me a message or an email saying "don't forget!" I understand that to him this is all a joke but A) it's a little off-putting that this is his reaction to something that clearly stressed me out and B) how do I politely let him know this game of his isn't funny and I'm over it?
I'm not asking to be coddled at all, I can handle my own anxiety and stress factors well enough. They don't affect my performance or my work and I was simply expressing initial gut reaction to him. I find his behavior childish. Neither of us are in a superior position over the other but he has been here longer than me and I don't want to come across as the "b-tchy newbie". He's also not being malicious about it, he clearly means it as a harmless joke, but at this point it's severely annoying. I'm currently the only one he is doing this to (that I know of) so it's not like a group of us can lodge a complaint. Is there a recommended protocol for dealing with annoying one-on-one coworker behavior?