As the mistake was performed because of the god Indra, he grants Hanuman a want that his system can be as potent as Indra's Vajra, and that his Vajra may also not damage him. In addition to Indra other gods have also granted him needs: the God Agni granted Hanuman https://www.tumblr.com/hanumanmandiradelaide/755795763365380096/inclusivity-in-worship