I think the reaction will depend on each character’s personality. Yes, most commonly someone would probably be uncomfortable or embarrassed, but if you want to emphasize how each character takes on different situations, some might act cold, get angry, make a joke/remark, laugh, etc. I think you should think about what type of character you’re writing about and base their reactions off that.
This also includes what it is taken as. Kiss or not, people each have their own opinions of what classify as a kiss. A person who is on the colder, angrier side of the spectrum may shake it off and claim that “nothing happened,” while a more light-hearted, emotional person would say that it was a kiss which is why is was extremely awkward.