What Causes Pain In Stomach After Injecting Methamphetamine?

My friend has been injecting meth for a month and a half evey once in a while his stomac and side areas hurt. Tonight he did a good shot and it is hurting him way bad its bad enough he might need to go to hospital. Why does it hurt. What. Could he do to make it go away orhelp with pain. I an 25 weigh. 145 and health is good as far as i now