The punch to Michael's face broke his cheek bone which gave him a permanent black eye (and caused his sinuses to continually operate - that's why the use of a handkerchief constantly) right up until he got back to The usa and experienced surgical procedures to repair it (Freddie states, https://bookmark-nation.com/story18643426/5-essential-elements-for-7-reason-why-the-godfather-master-piece