Yikes, after knocking him over the head, just see if it will heal it self, plants are amazing, maybe protect that part from the direct sun. Give it a try.

Yep, the prognosis isn't good, but I have seen it happen. The important thing is to keep the "wound" from moving more, and to keep it from drying out too much, without cutting off the air supply. A careful bandage with a few layers of gauze or cheesecloth will help do all three.

All is not lost - you can always put another one in. I did this last year and it grew very quickly.

I would try and plant the cucumber deeper in the pot so that the wound is below soil level.

Andrea, I think that if you plant it deeper it might rot if bacteria gets in, not really sure.?????

Planting members of the squash family (including cucumbers) deep is a good way to kill most of them quickly!