collisions

Hi, my name is Leandro.
My friends and I are developing a 3D game using Panda 3D. We are having some problems with the collisions. We use a sphere around our main character and activate the collision with geometry. The problem is that the main character is also a geometry, so the sphere collides with him and ruins everything.
Does anybody know how to fix it, or another way to detect collisions?
By the way, how many triangles has the panda model that we use at the tutorial? How many polygons the engine can handle with?

I really appreciate any help

Thanks a lot

Leandro