What did Lemech mean when he said to his wives "Did I kill a man to my wound or a boy to my bruise?"
Rashi #1 and Targum Onkelus: After accidentally killing Kayin (his great-great grandfather) and his son Tuval Kayin, following which his wives did not want to have relations with him, to appease them, he declared 'Did I kill a man by striking him deliberately or a boy by deliberately wounding him?'
Rashi #2 and Targum Yonasan: When, having born him three sons (and daughter), his wives, knowing about the forthcoming Flood, separated from him, he replied "Did I kill a man and a boy (Hevel, who was a man in stature, but a boy in years)? And if Kayin, who did, was granted a reprieve lasting seven generations, how much so will I, who did not!'
Seforno 1 : 'For (when) I killed a man (Lemech) I wounded myself, since the dead man was my (grand)fatherl and (when) I killed a boy (Tuval Kayin) I bruised myself, since the dead boy is my son'.
Ramban #1: Refer to 4:24:1:3.
Ramban #2: Chanoch, a highly intelligent man, taught his children all the Chochmos mentioned above (in Pesukim 20-22), including implements of war. Consequently, his wives were worried that he would be punished for plying his father's trade (that of murder). He therefore tried to assure them that, unlike his father, he had not murdered 'a man of his wounds or a boy of his bruises' (i.e. swords and spears are not synonymous with death, as there are ways of killing that are more painful than with a sword.
Da'as Zekenim (verse 15): "L'Chaburasi" means that it will cause my death, due to Hashem's promise to avenge whoever will kill Kayin.
The Seforno learns like Rashi's first basic explanation.