As the mistake was done by the god Indra, he grants Hanuman a wish that his system would be as powerful as Indra's Vajra, and that his Vajra can also not hurt him. Along with Indra other gods have also granted him needs: the God Agni granted Hanuman a desire https://claytonuvjjg.canariblogs.com/the-best-side-of-hanuman-51816425