Can I nurse a butterfly back to health?

I’ve found a butterfly in my garden with a slightly broken wing. I was photographing him when I noticed his plight. I held my hand out and he hopped on so I brought him inside and have put him on a plant. It’s rather cold and breezy outside so I’m a bit reluctant to just put him in the garden.

Could I nurse him better do you think and if so how? I have a bit of long standing fascination and love of butterflies and don’t want to just abandon him.