Why and how does verruca start! How do I get it off?

Surgery to remove. Warts are caused by a virus. They can be removed with freezing or surgical excision. See your doctor.
Verruca. Verruca: a wart by another name, a local growth of the outer layer of the skin (the epidermis) caused by a virus. The virus of warts (a human papillomavirus) is transmitted by contact. The contact can be with a wart on someone else or one on oneself (autoinoculation). Treatment is with salicylic-acid, nonprescription freezing, and rx by doctor-aldara, bleomycin, candida, liquid nitrogen, laser.