The punch to Michael's encounter broke his cheek bone which gave him a long term black eye (and prompted his sinuses to continually run - for this reason using a handkerchief all the time) until finally he bought again to America and experienced medical procedures to fix it (Freddie claims, https://throbsocial.com/story20661235/5-tips-about-7-reason-why-the-godfather-master-piece-you-can-use-today