I'm not an expert gardener but I think you just have to leave them in the ground as long as the roots are intact in the soil it will still grow. Just remove anything that can cause any harm to your plant.

Same thing happened to me, any advice?

I ended up leaving the onions in my garden. The tops continued to die off, and when the last top died, the onions started to rot in the ground. The onions that continued to grow were odd shaped.

i think you have a problem. when onions start to die back, you bend them over at the neck. this sends more energy into toughening the skins for better storage. about a week or so later you pull them. you are now in that stage even tho you did not do it. if you have any onions that were not effected then allow them to grow but the ones that have had their tops bent over at the neck, well treat them as if they were dying back and you bent them over.

tom