Is it too late to create a child theme

When I installed WordPress I didn’t know anything about it so have made lots of silly mistakes, like editing the main theme, not a child theme.

I’ve made quite a lot of changes (minor, but a lot of work to redo) and I don’t know how easy it would be to go back and create a child theme in retrospect so that they aren’t lost when I need to update. It’s taken a lot of trial, error and heartache to get to this stage and I’m not sure I could replicate my results without going through it all again!

Can anyone tell me how easy this would be to do, and whether it is worth doing at this stage?