I have had 2 serious cuts where I have lost feeling.
The first one when I basically severed the tip of my thumb. The flesh was stitched up and it survived. However, I have absolutely no feeling in the damaged area and that was over 20 years ago.
About 5 years ago I had a nasty over the bars and my eye shields cut deep into my face, lost feeling in an area above my top lip and couldn’t smile straight. This has gradually got better and the numb area has got smaller. The docs reckoned that it could be years before all the nerves make new connections and it might never happen at all.
So I reckon your answer is months, possibly years and maybe never.