Yeah on a photoperiod it would just be extreme topping but an auto well you have choices.
A, hope the stem mends
B, hope it recovers well ,veg for longer than normal and get some sort of harvest.
But honestly if I was you I'd get another seed dropped, and get that ready while you wait to see what happens to this one.
I feel your pain. Yesterday I had to cut what was my best prospect ever and six weeks into flower I find what I think are pollen sacs growing out of the buds, loads of em so I just cut it down to be as safe as I can