Unfortunately, the rules as written don't differentiate between armed and unarmed combat damage. Sorry. 
As for the damage of a punch, it is 1d3+ your Strength modifier. If you roll a Complete success (5-9 over the Target Number), damge is increased by +2. An Extraordinary Success (10+ over TN) gives a +4 to damage. This is explained on page 250 of the PG.
Former Decipher RPG Net Rep
"Doug, at the keyboard, his fingers bleeding" (with thanks to Moriarti)
In D&D3E, Abyssal is not the language of evil vacuum cleaners.