Take another look at the sentence:

Chet decided to get a huge Chinese dragon tattooed across his shoulder blades once the stabbing needle pierced his skin, however, Chet quickly changed his mind, opting to pierce an ear instead.

However is a conjunctive adverb that is interrupting the flow of the sentence. When a conjunctive adverb interrupts the flow of a sentence, it requires a comma both in front and behind it.

Go back to the sentence to try again.

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