Just weld it and forget it. I wouldn't worry about blocking the coolant off. Just weld it and forget it happened.
This is why some guys can never port heads for a living. If that little hole wrecks your day you'll hate trying to make money porting. If you are going to grind on heads and intakes you had better either know how to weld or make a welder your buddy. Or live with your port work running slow.
