After masturbation, semen is soaked by bedsheets, underwear and sometimes wiped with other clothes. is it okay to do so? is there any pregnancy risk if a girl touches it accidentally and then touches her vagina to itch?

Basics. Sperm are formed with limited energy supplies and an absolute need for a specialized environment. They can survive/function up to 6 days inside the mucous lining the inside of female genitals. They soon dry/become infertile/dissolve to nothing but debris if outside on clothing. If a glop of fresh semen is placed inside her genitals she can get pregnant.