I'm playing in a game as a warpriest sacred fist, i casted dimensional blade on myself. My GM said that the text of the spell makes it so that i cant target my fist because they are not in my hand. is this correct? unarmed strike counts as a weapon, i don't see why dimensional blade wouldn't work on them.
A Sacred Fist cannot use Dimensional Blade on their unarmed strikes because their Unarmed Strike class feature does not include the following:
A monk’s unarmed strike is treated as both a manufactured weapon and a natural weapon for the purpose of spells and effects that enhance or improve either manufactured weapons or natural weapons.
Unlike the Monk, a Sacred Fist does not count their unarmed attacks as manufactured weapons. Unarmed Strikes are not a valid target.
Attacks made with the weapon are melee touch attacks that ignore all armor. Force effects, such as mage armor and shield, still apply their AC against attacks made with a dimensional blade. Bludgeoning weapons used to make attacks with this spell deal half damage and are treated as slashing weapons. If the weapon leaves your hand before the end of the spell, the effect ends.
The question is more, do fist count as weapons in my hand, because the spell is written oddly.
No. You aren't holding any of your unarmed strikes or natural attacks in your hands. "Wielding" is more of a loose term, but "holding" is not. This spell works on any melee weapon which you can drop, easy as that.
I mean, a creature's unarmed strike is its entire body, so if Dimensional Blade worked on unarmed strikes your whole character would turn 2-dimensional for a turn. Which sounds very unhealthy.
That said, it wouldn't mechanically make much of a difference if your GM allowed you to use this spell to attack with your fists. Just as long as you ignore the implications of the spell effect.