It even looks like the hub threads are shot in that picture. Fortunately, it looks like your hub is fixed/fixed, yes? Flip it over, install everything carefully, and tighten it down really well, and you should be in good shape. It can take a little practice to get the cog and lockring just right, and it's definitely worth checking periodically through several rides after installation.

By the way, are you using a chainwhip and lockring tool?