Hi,
It depends on how fresh the sperm is. After ejaculation, sperm dies outside of the body within a few hours. If a person has sperm on their fingers after ejaculation and then immediately inserts the fingers into the vagina, there is a chance of getting pregnant. So the sperm on the door knob or bedsheets would have to be pretty fresh to get pregnant although it's not a great possibility. Obviously, it's always best to make sure he washes his hands thoroughly.
What if the sperm is dry on the door handle?
Or the door handle is dry but there could be a trace of little soerm not in liquid stuff though
Once dry, the sperm is dead.
You will not get pregnant from the above situations.