Lower back tightness

My lower back is constantly tight. It's fine when I'm warmed up and doing my workouts, or stretching, but otherwise there is no pain or soreness just a tightness.

I know that I have a weak core and am currently doing Abs 2 to build up my core strength. My thought process was that because I have weak abs, my lower back compensates and therefore works harder during my workouts. I've also tried to become more mindful to keep my abs engaged and tight during my workouts. I don't know if this is the correct solution.

If it continues I plan to go and see a doctor but it's difficult at the moment with Covid.

I was wondering if anyone on here has had similar problems and can give me some advice, or point me to a good online resource that I can use. I really want to get it better. Thanks in advance :)

Edited