Not much you can do but just be cautious. You can try to shield with the screen protectors but of course, that will distort all your photos. I guess you could also invest in a thick case, and hope that your lens won't come in contact with any sharp elements.
Even if you scratch the glass, it will still take perfect photos, the scratch will have no adverse issues with any photo's you take. There's a great threa here via search with info on this....too busy to find it though
As you can see in the photo the camera is protected as the case surrounds it. So if you set the camera down no way for it to get scratched. As long as you don't have your keys in your pocket with phone you're golden.