My friend told me to let it scab and don't let it get wet. Is this right?
Never soak your tattoo in water and never take advise from friends and family. They could be right but also could be very wrong.
You should ONLY follow the care instructions given to you by the artist that did your tattoo. They will be what your artist feels is the best way for you to heal your tattoo. Remember, they do this daily for a living. Your friends don't.