As the error was performed by the god Indra, he grants Hanuman a wish that his human body would be as potent as Indra's Vajra, and that his Vajra could also not hurt him. In conjunction with Indra other gods have also granted him wishes: the God Agni granted Hanuman https://www.evernote.com/shard/s419/sh/d662d02e-2c09-d5cd-3e70-5704caaa22e1/IK3YHJV17xXjWT1mdSDSWcmfLcqdAE7i_uX1peo6zzxbBq3iA_WsnJ0Ndg