Just like learning English, you just need to persevere.
I started practicing Taekwondo when I was 23 years old. I practiced Taekwondo for 2 months at that time, every day. My legs were almost in a straight line (and my waist hurt in the end).
But pay attention to the warm-up. If there is a strain, there are two situations (real experience): 1. There is a tearing feeling (serious). In this case, you need to recover and practice; 2. It is not very good. If it's serious and you feel you can tolerate it, you can continue practicing.
It is okay to warm up now, the rebound will not be severe.
Come on! no problem!