I'd some dark tones inside the nostril and the ear. And darken the shadows underneath the head and neck some, that'll make it look like he's being lit from above, give it a bit more depth, and it'll balance the darkness of the eye.

Until you"fix" it, you can protect it from smudging by covering it with tissue paper so nothing rubs off. If you're framing it, the glass will protect it, but if you roll it, definitely use the tissue paper.

And just sketching lightly in a landscape in the distance, or a fence and barn, just lightly, will keep it from looking so blank!