Answer:
The metaphor allows Sebastian's speech to be something painful, similar to a doctor who refuses to take care of a wound, but starts rubbing it making it more painful.
Step-by-step explanation:
The metaphor is a figure of language that allows a relationship to be established between two different terms, allowing one of them to assume the meaning of the other subjectively.
In lines 143-144 of "The Tempest" there is a metaphor that compares Sebastian's speech to a doctor who worsens a wound by rubbing it and causing more pain to the patient, instead of helping him. This means that Sebastian's words should help the king, but it is causing more pain and suffering than anything else.