The hole is not a leak. It is part of the carb system. The carb can only leak air from its mounting points to the intake/engine. Or it can leak fuel from the bowl. Anything around the mouth of the carb is supposed to be there and do what it is doing.
If fuel is coming out of that hole then your float and needle is not seating correctly. In addition to the new needle did you clean and polish the port the needle slides into? There could be some abrasion that is causing the needle to not seal. Is the float sitting correctly? If it bent at all it could be letting too much fuel in the bowl.