You can edit your posts on Mastodon, just click ⋯ and then "Edit". There is no time limit or editing limit.
If someone has already boosted your post, they will get a notification. This is to prevent any "bait and switch" abuse of editing.
Also to prevent abuse, people can see the edit history of your post. If you need to hide sensitive information posted accidentally, delete the post instead of editing.
More info and questions answered at:
