Before we explore more complex fixes, let's not ignore the easy solution that might exist - do you have another photo of his head, at the correct size and angle, that might be suitable for a swap?
I wonder if the images are appearing in a different order on your screen than mine? I see a couple of photos like that, but both are on the left, not in the middle.
Oh, wait, I see it!
Alas, the angle won't work
Yep, that's what I was thinking too. And it's easy enough. Just sample the sand colour with your eyedropper tool, then add a Solid Color layer of that colour, and set it to "Color" blend mode; then mask on carefully.