Yes, cutting the cane out is probably a good idea, but depending on the cause it might be best to remove the entire plant. Blackberry Cane Gaul is a bacterial infection which requires removal of the entire plant whereas Blackberry Knot Gall is caused by wasp larvae and is relatively harmless to the plant.
Internet searches are helpful with issues like this, but sometimes it takes someone with experience to make the correct call. I was hoping someone here might have that experience and be able to help me decide what to do. We’re coming off a holiday weekend, so many of the regular contributors to this forum may not have been active here for several days.
As a side note, I am waiting for a reply on this question from my local Cooperative Extension and see that the Master Gardener initially assigned the question has passed it on to the Extension Agent. From this I assume it’s a difficult question to answer. I’ll post an update when I hear from them.