Focus on the wounded mercutio words to romeo. what pun is in these lines? what is implied by his choice of words?

Mercutio's dying words use a pun on the word "grave."

He says, "ask for me tomorrow and you shall find me a grave man." On the one hand, he means that tomorrow he'll be serious, or seriously injured; on the other hand, he means tomorrow he will be literally in a grave.

Mercutio is implying that, despite the wound's small size, it is a fatal wound that will kill him quickly.