Bootstrap follows common web standards and—with minimal extra effort—can be used to create sites that are accessible to those using AT.
If your navigation contains many links and comes before the main content in the DOM, add a Skip to main content link immediately after your opening <body> tag. (read why)
When nesting headings (<h1> - <h6>), your primary document header should be an <h1>. Subsequent headings should make logical use of <h2> - <h6> such that screen readers can construct a table of contents for your pages.
Learn more at HTML CodeSniffer and Penn State's AccessAbility.