Blender Help

I'm not a Blender expert so if anyone has better advice please chime in. But I would merge vertices to close the hole. Pick the vertices you want to merge, press "W" on your keyboard, choose the "merge" function. It might mess up the shape or curve of the sim's chest. You could also add new faces but I've found that adding new faces tends to mess up the UV map. Again, if someone has a better answer please post.

And you may know this already, but be sure to edit the specular since likely the spot where the badge would go will be shinier than the shirt, and you'll want to edit the bump map too.