Yes, you can block specific countries from accessing your website by modifying the .htaccess file located in your "public_html" directory.
Please refer to the following link, which will allow you to select the country (or countries) you wish to block. This website will provide you with the exact code that must then be added to your .htaccess file, saved and uploaded to your account.
http://www.countryipblocks.net/country-blocks/htaccess-deny-format/
There are additional ways to deny visitors for those that have more advanced applications and/or programming knowledge.