Can't create a database in Ruby on Rails

I'm following some tutorials of association in rails database, the first step is to create the app with rails new newProject -B. Then i create the two models with rails g scaffold Father name:string and rails g scaffold Child name:string sex:string father:references.

After that i try to create the database with the command rake db:create, but an error appears:

Could not find nokogiri-1.6.7.1 in any of the sources Run bundle install to install missing gems.

I run the command bundle install normally, but when i tried again, the same error appears. I tried to insert in the GemFile gem 'nokogiri', '~> 1.6', '>= 1.6.7.1' and the same error persists.