Minecraft Forge error You need to run the version 1.7.2 manually at least once? How do you do that?

In the bottom left corner of the Launcher you have the profile section. Create a new profile and select 1.7.2 as a version.

Edit: Forgot the launcher has changed now. Click the button at the top right and then launcher options, from there click the + and select 1.7.2 in the versions

It says 2.1.1217?