Worm inside stem of weed

Thanks for the friendly advices, I dont know which type of worm it is, I will try to fix it without pesticides

Any worm inside the stem of your plant is a bad worm. You can try Rap-a-cap's wire method while being very careful not to cause more damage to the plant. Some worms only burrow into the stem to lay eggs so they will be closer to the entrance hole. Worms that eat the plant will dig tunnels as they move through the plant and will soon be too far from the entrance hole to find. Be VERY cautious inserting or injecting any pesticides INTO the plant. This bypasses the plant's external defenses and puts the herbicide directly inside the plant so what is a safe concentration sprayed on the outside of the plant can harm it by injection. Also, the "juices" inside the plant are what is growing your bud. That herbicide then has a direct path to your bud and your lungs.

What kind of worm? Leaf miner, earth worm, maggot, cabbage leaf looper? There are good and bad worms