We don't want users to delete their question after they have received an answer. This is because that deprives the answerer the chance to get the reputation bonus they deserve for their work. Somebody considered the question worth answering, and after that point the community should decide whether the question is worth keeping. This applies equally to the answers. While the things you post are your intellectual property, the site legalities (you approved of the terms of service by posting) mean that we get some rights to the posted copy, should we want to keep it.
There are many reasons why a user might want to delete the question. Noticing that they asked an uninteresting variant is one of the better ones. But more typically (?) a self-deleter is someone who wants to cover their tracks - like a student who doesn't want their teacher to see that this question was answered in the internet.
The rule exists to keep users from abusing the possibility habitually. The details of the question-ban threshold are kept a secret, so that such users cannot game the system by skirting at the boundary. It is clear that you had no such motives, but the answer to your question has been upvoted.
My advice to you is:
- Roll back this question to match the version that was answered.
- Ask a new question. Possibly add a link to the older version. That way everybody will see that you noticed that you really wanted to ask something a bit different, and everybody will be happy.
One final remark. If one notices that the posted version of a question was obviously wrong then one can edit without worrying about stepping on the toes of the answerers. In particular if the OOPS-moment comes within the five minute grace window. In those cases the would-be-answerers usually comment anyway. The quickest draws may already have started typing answers, but they deserve, IMHO, very little sympathy.