As the error was accomplished because of the god Indra, he grants Hanuman a wish that his body might be as robust as Indra's Vajra, and that his Vajra can also not harm him. In addition to Indra other gods have also granted him wishes: the God Agni granted Hanuman https://sites.google.com/view/hanuman-temple-adelaide/exploring-the-spiritual-heart-of-adelaide-hanuman-mandir