Does a pinhole camera use convex lens?

No. It's way of working is different http://en.wikipedia.org/wiki/Pinhole_cam...

Yes a tiny one, it it were concave it would make everything smaller

A pinhole camera has NO lenses! Just a pinhole, as the name implies.
No lens is required because the pin hole creates a point light source. Of course if you want to control the image size other than by distance from the pinhole then you can use lenses.

no a pin hole is just that a pin hole

A pinhole camera has only a pinhole, no lens at all.
The size of the picture will depend on the focal length. (The distance from the pinhole to the film). A long focal length creates a telephoto effect.
A pinhole creates tremendous depth of field. Everything, regardless of distance from the camera, will be in focus.
The disadvantage is that the pinhole allows only a small amount of light to enter and requires LONG exposure time.
Lenses were developed to solve the problem of focusing the light when the hole (aperture) is large enough to reduce exposure times to an acceptable duration.