Can I boil a peeled egg again?
I poach eggs, remove and chill them in an ice water bath to stop the cooking and then 'reheat' them in the simmering/boiling water right before getting ready to nap them with hollandaise and then serving them. (to aid in creating mass quantities of eggs benedict to be served at the same time) 

I suspect that you can further cook your under-cooked hardboiled eggs with no adverse effects (even AFTER peeling) in the simmering/boiling water. Hope this helps.