As the error was accomplished by the god Indra, he grants Hanuman a desire that his physique might be as strong as Indra's Vajra, Which his Vajra can also not damage him. As well as Indra other gods have also granted him needs: the God Agni granted Hanuman a wish https://shabarmantra48260.blogocial.com/little-known-facts-about-hanuman-72759580