You can delete your own questions, assuming certain criteria are met.
From our help page Why are questions deleted:
Users can delete their own questions if the question:
- has zero answers
- only one answer, but that answer has no upvotes
Simply click the delete link underneath the question.
Deleting a question when it has upvoted answers is unfair to the person who took time to answer the question with a good quality (upvoted) answer. There are many good answers to what are, at a glance, "bad" questions.
Many questions are not actually bad, but are instead misguided. A good answer can help more than the original questioner, it can help a thousand more people who might have the same understanding. Would you deprive a thousand more people from having the benefit of the answer you go simply because you feel a bit daft in hindsight?
There are no stupid questions, only people too proud to ask them.
As an aside, there was some abuse of the question/answer format of the site in the past in the form or people deleting their questions. Someone would ask a "dumb" question, get a good answer and then immediately delete their question before the downsides came in.
It's not much fun investing your time answering a question when OP is just out for themselves.