How serious is a having a herniated disk?

Depends: It depends on size, amount of inflammation, location (neck, mid back, low back, against spinal cord, against nerve but not cord). Sometimes it keeps nerves or spinal cord from working properly. Other times it causes pain. Sometimes it is silent (no symptoms, problems). Most improve with time. Treatment depends on how severe the symptoms are, whether or not they are worsening, & how long they last.

Depends on symptoms: They range from nothing leg pain buttocks pain if tit is not bothering a nerve forget about it if you are not having leg pain then it is not bothering a nerve it is a MRI finding not a diagnosis.