It's this line, "And with forc'd fingers rude" - this is called a broken line or a half-line, and this broken line has been read, I think, rightly as Milton's indication to his reader that he's not even up to the task of writing a sonnet at this point.

是这句，“我不得已伸出我这粗鲁的手指“,-这叫做断裂句，或者半句，将这句理解为,弥尔顿向读者暗示他此时甚至,还不能写好十四行诗是正确的。

耶鲁公开课 - 弥尔顿课程节选