As the mistake was done via the god Indra, he grants Hanuman a wish that his physique would be as solid as Indra's Vajra, Which his Vajra can also not hurt him. Coupled with Indra other gods have also granted him needs: the God Agni granted Hanuman a want that https://indiantemplesnearme.blogspot.com/2024/12/hanuman-mandir-and-shani-dev-temple-in.html