As the error was performed from the god Indra, he grants Hanuman a wish that his system would be as robust as Indra's Vajra, Which his Vajra also can not damage him. Together with Indra other gods have also granted him wishes: the God Agni granted Hanuman a desire that https://sites.google.com/view/hindu-temple-south-australia/hanuman-ji-mandir-adelaide-blessings-devotion