Other mistake: When the film starts, Dolittle drinks from a yellow cup, the angle changes to behind his shoulder and it's perfectly obvious the cup is empty. Then, despite this, he keeps sipping and moving his mouth all the time.
Continuity mistake: When the pigeon defecates on the doctor's face, the poo falls on the side of his mouth. Half a second later the mouth is clean and the poo is all over his chin, nowhere near where it fell before, so it couldn't have slid down there.
Continuity mistake: When Dolittle arrives at the woods, right before he parks, the side of his car is totally dusty and dirty. When he steps off, after a change of angles, it is spotless.
Answer: Geno deliberately broke Mark's nose during the party after Mark made a snide remark. After the party, when Mark suggested a way to have John committed and still get their money, Geno had enough of Mark's ignorance and punched him in the nose again to add further insult to injury.