Pain you are experiencing is root pain due to compression of nerve when it is exiting from vertebrae. It is postural in nature due faulty posture. Faulty posture leads to strain over para spine muscle, which further compromise neural canal that leads to nerve compression. You can use muscle relaxant with or without pain killers and Physiotherapy.

This symptom appear when there is a nerve compression in your lower spine, it would be better if u get it investigated

Lower back pain radiating to legs can be a sign of nerve compression in lower back, most commonly due to a disc issue- needs confirmation with examination findings.

Check ur posture and regular back strengthening exercises