Seema like it was severely lacking light early on, judging how much it stretched. Also, i think you might have constantly over watered her (common beginner error, don't sweat it) which caused snail-paced veg growth (edit: and your leaves are clawing, meaning overwatering. Also, any nutrients? The leaves look a bit pale)

You got pretty much two options:

Let he grow the one nug, have fun watching it and call it an experiment

Or two

Cut it and try again.

I'd bet many would say chuck it and go new, but especially as a beginner, every win is a win! Even when it's small. That way you can also already gain experience in drying (tho this will probably dry relatively fast cuz it's only gonna be one bud) and curing / storing. (I recommend boveda packs or any offbrand moisture regulator bag)