I don't know why but I heard it could does anyone know?? I want to get mine done but I have to reassure my parents I know the risks and I knew all about them until my dad brought up this one...

You're just talking about your belly button right? Because if that's the case, how in the heck would your midsection go numb?? I mean maybe if you were piercing your spine! It's just a little flap of skin-the same as getting your ears pierced. But if you do get it done, make sure you go to a GOOD piercer person-get recommendations because not all people who do piercings should be doing it-the should actually be certified or have some kind of knowledge of what they're doing. I've known too many people that have gotten pierced and they did it too shallow and it ended up ripping out, not a pleasant feeling, or a nice sight.
You can reassure your dad that other than a tiny bit of blood (if that) and a cute little belly, there's nothing to really worry about.

It can go numb because some places use numbing spray so when they pierce it it won't hurt. I had the spray on mine it didn't hurt and the effects of the spray wore off after half an hour.