Single word for people who are like "a frog in the well"

Is there a single word describing someone who is like a frog in a well? The frog believes the well is the entire world. How can I describe people who think that their own small environment is the entire world?

Synonyms of parochial, "characterized by an unsophisticated focus on local concerns to the exclusion of wider contexts", may serve. Such synonyms include confined, insular, limited, local, narrow, narrow-minded, petty, provincial, regional, small-minded, isolated.

Insular, for example, has a sense that means "separate or isolated from the surroundings; having little interaction with external parties; provincial." Narrow-minded and small-minded are of course easily understood, and so would be close-minded.

Blinkered, fitted with blinkers, or "eye shields attached to a hood for horses, to prevent them from seeing backwards and partially sideways", is another possibility, as are formations from synonyms blinders and winkers.

Edit: Also consider monomania, "excessive interest or concentration on a singular object or subject" or "a pathological obsession with one person, thing or idea"; obsession, "compulsive or irrational preoccupation; an unhealthy fixation"; idée fixe;
tunnel vision, "an extremely narrow point of view; narrow-mindedness"; and locked-in.

I would add myopic to @jwpat7's excellent list.

One term you could use is isolationist, although isolationism is used mostly to describe countries who do not interact internationally and focus on themselves. It might be understood when used to describe people, however.

Depending on how far you want to take your analogy, you could label the frog a solipsist.

I believe "provincial" is the best match for what you are asking for, but only if you want a pejorative term. Although, I find it hard to imagine making this observation about someone and it not being intended pejoratively.