I had the same exact problem as you during my first grow. it was a long, red, thin stem just kind of lopped over to a side. What kind of soil r u using? and in what kind of pot is it in? as a new grower, you will most likely overwater your plants, which will slow your plant the fuck down. just give it about 100mL every day for the first few weeks and it should be happy. a fan lightly blowing on it will help the stem. the stems gonna be like "nigga what the fuck r u doin blowin at me all the god damn time, imma get my stem on swoll so you u wont b doin shit to me nigga" so when the stem is thicker, it will suck up the nutrients/water from the soil up much more effectively next time and probably even survive an overwatering every now and then.
you should add some more soil to the plant too so the stem is surrounded by soil left and right and wont lop over. if you cant get it to stick straight up now, it will stay crooked for the rest of the plants life.