No. But if he flicked his booger, then went over and touched it after it left contact with his body, THEN it might turn to gold. The same is true when he pees. It’s just normal pee (though perhaps a bit more golden than most of us), and stays that way. Keep in mind that not everything King Midas touches turns to gold. The air around him doesn’t (otherwise he couldn’t breathe). If he put his hand in the Atlantic Ocean it would not turn the entire ocean to gold*. If he eats food with his hands the food turns to gold before he gets it into his mouth. But if he uses a golden fork he can eat normally. He can’t use a napkin, though, because the napkin turns to gold and then it can’t be used to wipe his mouth. He can drink, but only through a gold straw.
*Midas eventually was cured by washing his hands in the river Pactolus. When he touched the waters, his power flowed into the river, and the river sands turned into gold, and Midas was free.