I masterbated and after few minutes probably less than 4 minutes i touched the doorknob to open the door with my shirt to be safe, my shirt had small amount of sperm. after i opened the door a females touched the doorknob. is pregnancy possible here?

Of course not.

Your sperm was rendered dead by the time you opened the door. Sperm dies in minutes when on objects, it only survives in vaginal fluids or in a sperm bank. No sperm entering the vagina will not cause pregnancy. In the future be aware of safe sex and how sperm can cause pregnancy.

No. The sperms die within 10 mts after ejaculation if not in the vagina