'How to' vs. 'How do I'

In the original context, how to correct this error was intended as a question, but this is not a standard way to ask a question. It isn't a sentence, nor is it an interrogative, and it shouldn't have a question mark at the end of it. It's a content clause, or what is misleadingly called a "noun clause." Content clauses of this type would typically be used in contexts like:

• I wonder how to correct this error.
• There's no information on how to correct this error.
• How to correct this error will be the focus of my talk.

Content clauses like this are also often used by themselves as headings and occasionally by people musing to themselves (e.g., "hmmm... how to solve this...").

"How to correct this error?" is missing a subject and a (finite) verb. So any of the following, or many variants, would look more complete as questions:

• How do I correct this error?
• How would you correct this error?
• How might one correct this error?