Run the RVM command to use your new Ruby installation. Run the command which ruby to make sure it's pointing to somewhere in ~/.rvm/, and not to /usr/bin/ruby.
$ rvm use 1.9.2
$ which ruby
/Users/uzimonkey/.rvm/rubies/ruby-1.9.2-p0/bin/ruby
By Michael Morin, About.com Guide
Run the RVM command to use your new Ruby installation. Run the command which ruby to make sure it's pointing to somewhere in ~/.rvm/, and not to /usr/bin/ruby.
$ rvm use 1.9.2
$ which ruby
/Users/uzimonkey/.rvm/rubies/ruby-1.9.2-p0/bin/ruby