Remove facebook like/share button

i saw that is a pluginButton which is located inside your wp admin page you can stop or delete the pluginButton to remove that at the top left or what other settings you want ..

It’s not a feature of the Twenty Twelve theme, so it’s more than likely a plugin. Go to your installed plugins (Plugins → Installed Plugins) and see if you can find a plugin for Facebook Like. Shouldn’t be too hard to find, although it might be bundled in with another plugin.