This is characteristic of a muscle spasm and it is extremely common in your age group. Please Expect it to last a couple of weeks at least. Take T. Myospaz-Th twice daily after food, that should help take edge off the pain a little bit, but dont expect it to go away before the affected muscle heals fully. To avoid such muscle pulls during workouts, please do 'warm up' exercises as a part of your routine, your gym trainer might be able to help you with specifics.
In rare instances if low back ache persists, you might need to visit your family doctor once to decide if you need a specialist consultation. Hope that helps.
Next Steps
Take T. Myospaz-Th twice daily after food