The punch to Michael's encounter broke his cheek bone which gave him a long term black eye (and brought about his sinuses to repeatedly run - consequently the usage of a handkerchief constantly) right up until he got again to America and had surgical treatment to fix it (Freddie states, https://tetrabookmarks.com/story18827560/how-much-you-need-to-expect-you-ll-pay-for-a-good-the-godfather