My 5 yr old son has a wart on his hand and i took him to get it frozen, now it looks like it is turning black. is that normal?

Yes: When we treat warts with cryotherapy we are causing frostbite on purpose. The treatment works by disrupting tissue that contains viral particles and letting those viral particles get exposed to the body's immune system. The immune system makes antibodies that kills the virus, and then the wart goes away. It takes more than one treatment. The black wart will fall off, but that is not the cure.

Normal: As the skin cells die, the wart can become blackened before the it falls off, or sloughs.

Can also blister: They can often blister up also, but usually after turning black they will fall off.