Why would I have new left buttock pain daily?

It varies. The pain could be from different sources including a pinched nerve or compressed nerve root, muscle spasm, or from the hip. Your doctor can take your history and examine you to try and find out why in your case.
Buttock pain. Can be coming from various sources: often, the lumbar spine can be the cause with nerve irritation and possible facet degeneration on that side, sometimes with alittle instability. The sacro-iliac joint can be the cause, or a muscle in the buttock that got stretched or worked during some type of activity. The hip joint is usually not responsible for buttock pain. Try walking and some nsaids first.