As the mistake was done from the god Indra, he grants Hanuman a wish that his body will be as robust as Indra's Vajra, Which his Vajra could also not harm him. Together with Indra other gods have also granted him needs: the God Agni granted Hanuman a want that https://connerxjmpj.blazingblog.com/36992348/little-known-facts-about-hanuman