Cursed Wound (Ex)
The damage a clay golem deals doesn't heal naturally and resists magical healing. A character attempting to use magical healing on a creature damaged by a clay golem must succeed on a DC 26 caster level check, or the healing has no effect on the injured creature.
So my question in how is this handled, is it a check per wound (i.e. if a PC is hit 3 times for dmg the cleric needs to make 3 checks), or is a one time check( i.e. one check is good enough so the PC can receive healing for the total dmg from the fight.)
Only that PF doesn't work like that as it does not specify hit zones or similar.
You have a pool of hp describing your overall condition. If you're applying a cure spell you heal the number of hp rolled by your healer regardless whether you've been hit 4 times for 9 damage or once for 36. Thus it's one check for the spell you cast which then heals the hp you've rolled.
Per magical attempt to heal the damage.
This does require you to separately mark down damage caused by a clay golem from other creatures, but it's not so cumbersome.
Damage caused by other creatures can be healed normally, but this damage caused by the clay golem would require the caster check each time.