Can't the pen cap come off?

Please see if there is a plastic inner layer in your pen cap first. If not, please ignore the following answer. If not, please continue reading. The pen body is stuck in the plastic inner layer. Because your pen broke the plastic lining when it fell, you can't fix the pen body. This plastic inner layer is usually fixed in the pen cap with an internal screw. Insert the tail end of the pen body or other tools into the pen cap tightly, and rotate counterclockwise to take out the plastic inner layer from the pen cap, then wrap and fix the cracked inner layer with transparent tape (not too thick, otherwise it can't be put back into the pen cap), and then rotate and fix the plastic inner layer in the pen cap clockwise by the above method.