This is somewhat similar to this question with a subtle difference. He was asking mainly about questions without answers and I'm curious about questions like this where the OP has nudged in the comments somewhere that a post has answered his/her question but hasn't marked it as so. I see this often with low-rep OPs. Should there be something done about this? I feel like the solution isn't the same as in the original question posted as these questions shouldn't be deleted, but shouldn't they be marked closed at least? Is there some sort of standard thing to do on the SE network with this type of dealio?
Questions are not closed to indicate that they are "done with". They are closed to indicate it's not an appropriate question for the site, to prevent answers from being posted, and to enable deletion of the question.
None of which are suitable for the question at hand. It's a decent question with a decent answer. This answer has a positive score, which tells the system to consider the question answered. No further action is needed. (I edited the title and tags, though.)
Also see the discussion in People who do not accept answers; suggestion for dealing with this.