This is a feature request for exactly one (1) notification when:
- You've posted an answer to your own question before the 48-hour self-answer accept time limit, and
- You have not accepted any answers on that question, and
- The time limit is up and you can now accept your own answer.
Given the relative rarity of self-answers, and the presumed common intent of posting a self-answer in order to accept it, I don't think this will lead to unwarranted notifications as long as the above rules are precisely obeyed.
Two days is a good bit of time to wait, and right now if you intend to accept your own answer, the only way to track it is to either put it on your calendar, or bookmark the post and periodically check it. A notification would get rid of the guesswork.