I posted a question but realized there was more to it than I thought. A lot of answers are now invalid because the detail was not included. What should I do? I would delete it and make a new question but it says I can't delete now that there are answers.
Why do you need to delete it? Accept the answer that best solves the initial question, then create a new question that incorporates your new requirements (and any ideas you've learned from the existing answers to avoid anyone duplicating effort). The initial question still might be useful to other readers that don't have your additional requirements, even if it is no longer 100% relevant to you.
Oh, and don't go bug answerers of the other question to go look at your new question. If they found your first question, they'll find your second one, too.