If you do nothing, the plant/branch will continue to grow as though nothing at all has ever happened.
Cannabis is a remarkably tough and resilient plant and its powers of recovery are incredible.
I have had stems hanging by "threads" that continued to grow as normal, even though more than 75% of the branch was ripped/torn - I really must post some pictures of this to illustrate how incredible cannabis plants are.
Anyway, whatever you do, do not put tape on it or cover it with anything, this can just cause issues with mould/fungus, due to moisture building up underneath any sort of applied cover.
Really, in this case, do nothing would be my advice, the plant will heal itself perfectly.