If a Goblin PC has the "Hard Head, Big Teeth" racial trait, do they modify their bite attack modifier to deal x1.5 damage or leave it at x1.
Example: STR Mod=2 Bite +5. Deals 1d4 + 2
Bite +5 Deals 1d4 +3
Per the rules on natural attacks, creatures add 1.5x strength modifier to their natural attack if they have only one natural attack. The relevant quote from the above link is:
If a creature has only one natural attack, it is always made using the creature’s full base attack bonus and adds 1-1/2 times the creature’s Strength bonus on damage rolls. This increase does not apply if the creature has multiple attacks but only takes one.
The Hard Head, Big Teeth trait for goblins doesn't change this. If your bite attack is your only natural attack, and you don't try to combine it with your normal weapon attacks, it'll get 1.5x strength modifier to its damage.