WWW,
I regularly read the AAIB monthly accident/incident bulletins, and in my estimation about 50% of the reported GA incidents happen during landing and involve nose wheel failure etc. and only about one a month (if that) involves a solo student. GA pilots with more hours than you can shake a fist at are still doing it, so don't worry about your own abilities as an instructor.
Get him up solo again, as soon as you feel it's possible, a few successful solo circuits will make you both feel a lot better.
Hell, it nearly happened to me recently, I was flying back into my local airfield on Sunday, windshear threw me at the ground, I bounced twice before I'd got full power on for go-around, circuit practice for me next time!! Moral = You never stop learning.