Unless you never kiss anyone, there is always risk. HSV1 is incredibly common and most people with the virus don’t have any symptoms. HSV1 testing via IgG also isn’t very accurate, missing up to 30% infections based on studies done last year.
Did the kiss you shared with someone who knows they have HSV1 infect you? Hard to say. It really isn’t a risk that is easy to assess since people shed the virus without any outbreaks.
I think you shouldn’t worry in the least. If you get symptoms in 3-10 days after the kiss, see a doctor. Otherwise move on.
And just a little bit of advice. This guy knew he got cold sores and told you (albeit after). A lot of people have no idea they have it. So unless you plan on never kissing again or only kissing someone who has an unreliable negative HSV1 IgG test, I would let go of this worry.
The only way to truly protect yourself from HSV1 is by not kissing anyone. Ever. Doesn’t sound like much fun, eh?
if your partner doesn't have cold sores on his lips, you're maybe not at risk of contracting the virus . But, the virus sometimes spreads without revealed symptoms. You can still kiss him, but don't do that when he begins to experience tingling, itching or burning sensations. These can be some first symptoms of a new outbreak. You'll have a high risk of getting the virus if a new outbreak occurs. Also, be careful with oral sex because the virus can cause genital herpes. You should have a conversation with your partner, tell about your anxiety and how to prevent the virus from spreading. If you're always worried, this may interrupt your relationship.