It's common muscle strain ,reduce with rest when the day passes ,if it is severe take hot or cold pack, even persistent meet orthopedic surgeon

Hello, sudden onset of low back ache can be due to a muscle spam ,strain or slip disc at your age.  All the three causes can occur without any noticeable trigger or incident. If your pain is localized and you are not having any pain down your legs or numbness/ tingling sensation , you might be just having spasm. Take bed rest for a few days with some gel to apply to the back. If your symptoms does not subside in a day or two, consult an Orthopaedic surgeon