Continuity mistake: When Tifa first shows up to the scene at the ShinRa Monument, she looks over to see Denzel standing and her hair has fallen over her shoulder. When it cuts to a closer shot of Denzel (still over Tifa's shoulder), her hair instantly moved back.
Continuity mistake: When Yazoo jumps/flips over Cloud's motorcycle in the opening chase sequence, the way his motorcycle is flipping through the air changes slightly between shots.
Continuity mistake: When Loz/Yazoo/Kadaj are summoning the creatures to attack Cloud in the beginning of the movie, the number of creatures changes between shots.
Answer: The bullet bounced off and thereby did not directly hit him. As Kadaj's gang were after their "mother", you can be sure Yazoo did not intend to kill Cloud yet, so he must have aimed for the goggles. It's impossible for the bullet to graze his forehead in that angle, even though Yazoo could have calculated that, too.