It's my 3 weeks after discectomy it's that normal my back is still sore?

Disk Surgery Recover: The operation is to take away leg pain from the herniated disk. The pain you are experiencing is muscular pain from the surgical opening. This usually takes 8 weeks or so to resolve.

It can be as the : Surgical approach was through the back musculature and into the affected disc. Generally, it is a 6 to 12 week recovery period with return to unrestricted activity/ sports by 12 weeks assuming typical good outcome in a non smoker with the primary pain being leg pain preop, not back pain.