As the mistake was accomplished by the god Indra, he grants Hanuman a want that his overall body could be as solid as Indra's Vajra, Which his Vajra also can not harm him. Together with Indra other gods have also granted him needs: the God Agni granted Hanuman a desire https://bentdirectory.com/listings13340518/the-smart-trick-of-hanuman-that-no-one-is-discussing