There is a bump on the back, if it does not hurt or itch, there are several possibilities: a. It may be a common wart. The common wart is a viral infection in the stratum corneum of the skin, causing hyperplasia, keratotic hyperplasia, without pain or itching. Third, it may also be due to other causes, such as dermatofibroma. Dermatofibromas occur beneath the skin’s stratum corneum and above the stratum granulosum, and are a manifestation of skin cell variability. The variability is mainly manifested by abnormal hyperplasia and a solid texture.