The Book of Jasher 27:1-9 describes the death of Nimrod by saying that there was jealousy between him and Esau, the son of Isaac and brother of Jacob. Both of them would hunt in the same field and one day Esau saw Nimrod and his companions coming, hid, and then jumped from his hiding place catching Nimrod by surprise and killed Nimrod and his companions. It says "and (Esau) drew his sword, and hastened and ran to Nimrod and cut off his head." (*The Book of Jasher is an apocryphal book referred to in Joshua and First Samuel.)
There are a number of traditions as to how he died.Some say that he was killed by wild animals and others say that Shem, the son of Noah, killed him because he was leading the world into idolatry.The Jewish Encyclopedia states that Nimrod lived a wicked life as one of the world's first emperors. An angel from God appeared to him and strongly urged him to repent.
"But Nimrod declared that he himself was sole ruler and challenged God to fight with him. Nimrod asked for a delay of three days, during which he gathered a considerable army; but this was exterminated by swarms of gnats. One of these insects is said to have entered Nimrod's nose, reached the chambers of his brain, and gnawed at it."
Nimrod would die after 40 years of struggling with the pain from the gnat embedded in his nose..