Depending on the severity of the stress fracture, a splint or cast may or may not be needed. It just depends on the location, and how close the fracture is to becoming a full on break.
Generally, you can take some anti-inflamatories, try and stay off of it as much as possible, and it will heal on its own. But it does take time. Sometimes longer than an actual break.
Can we get a more specific location of your pain? Also, does it hurt if you massage the bottom of the foot, or just pressing against various bones?