How to tell this guy that I'm not comfortable with PDA yet?

We met few days ago in a Language Exchange meetup, it was a great night with everyone we all went partying later and the guy and I hooked up. Him and I ended up alone until 6 am just watching the sunrise, talking and kissing (like a lot of kissing). It felt great to me. He mentioned that he is a relationship type of guy while we were talking, and I was honest that I'm not sure but open to possibilities. We exchanged numbers and kept in regular contact since then (being kind of romantic). And today is another meetup and we're both going (separately). It seems that I'm gonna keep seeing him there regularly and I just don't want our very early relationship to cockblock other people from approaching me because the point of these meetups IS for expats to meet new people. Otherwise I'm more then okay to be intimate when we are alone, until we make it official.
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Just bare in mind that he is 24 and I am 33 (shy).
How to tell this guy that I'm not comfortable with PDA yet?
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