You're correct, trying to cut out the mark won't cure the curse at all! Actually, it'll make things worse! The mark will become infected very easily and spread the bruise up the wrist to the forearm so any sort of healing magic to stop the immediate damage would be smart.

When the mark is initially cut it can be cut out like a normal sickness might be, leaving the normal flesh underneath. But the mark will appear moments later and start to fester and grow again.

For this specific action, you may pick: Cutting the mark will accelerate the rate at which Arbert has nightmares which he'll have more frequently or heavy fatigue will set in that will make his body beg to sleep.