YUM I love peanutbutter and banana sandwiches mmm!
But about the knife lol... the smudge is probably just a water spot from when it dried. You washed it w/ dish soap so it was clean. My mom puts her food directly on the counter all the time and I freak about it lol but she would have made her sandwich ON the counter and she's always fine. A little tap from the tip of the knife is nothing lol.
Hope this helps and that you enjoy your yummy sandwich! Now I want one and don't have any pb or bananas LOL!
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