The lesion is called molluscum contagiosum.
Molluscum contagiosum is a common viral infection caused by a poxvirus which can be transmitted sexually or from contact with fomites (objects). Most people with the infection do not have noticeable symptoms although sometimes the lesion is a painless bump which may itch or become irritated. Usually a molluscum lesion will heal without treatment.
Molluscum is transmitted primarily through direct skin contact with an infected individual. Fomites have been suggested as another source of infection e.g. from bath towels, tattoo instruments, and in Turkish baths.
The molluscum contagiosum virus produces a papular eruption of umbilicated lesions which are discrete, smooth, and dome-shaped. They are skin-colored and contain a white, waxy, curd-like core.
It is a self-limited disease, which, left untreated, will eventually resolve on its own.
If the lesion becomes bothersome, then it can be removed by a dermatologist using cryotherapy, a scalpel, or chemicals.
In general, you can contract most STD's from urine, saliva (spit), semen, vaginal secretions, blood, and breast milk.