[Chekov isn't bothered by kissing friends and relative strangers. It's not a particularly Russian thing to do, but mistletoe days are relatively benign (the complications that arise from them usually don't have much to do with the bots, after all) and he's disinclined to worry too much about a little forced smooching.
And hey, there have been some very nice kisses with people he wouldn't have kissed otherwise. Why would be go out of his way to avoid those?]