As the mistake was performed by the god Indra, he grants Hanuman a want that his entire body might be as robust as Indra's Vajra, and that his Vajra can also not hurt him. In conjunction with Indra other gods have also granted him wishes: the God Agni granted Hanuman https://hanumanshabharmantra71478.blogofchange.com/37682012/details-fiction-and-mohini