“a thorn that goes into the hand.” As a drunk stumbles around and gets a thorn in his hand, thus hurting and embarrassing himself, so too a fool cannot grasp the proper sense and application of a proverb and ends up making a fool of himself with it.
There are some commentators and translators that nuance the verb “to go up,” and interpret it as meaning that the drunk picks up a thorn bush (instead of a “thorn;” the Hebrew can mean either one), and then hurts others with it. According to that interpretation, the drunk hurts others with the thorn bush and the fool hurts people with his proverb (cp. CJB; HCSB; NAB; NIV; NLT; and Bruce Waltke, Proverbs). Although that might be true, it is stretching the Hebrew meaning of the verb, and it is not necessary to do that since understanding the verse as saying that the drunk and the fool are both hurt by what they do makes good sense.