It could be a wart.

Common warts (ichthyosis). Also known as thorns. The rash is a soybean-sized or larger grey-brown, brown or normal skin-colored papule, with a rough surface, hyperkeratosis, hard and papillary appearance. It usually occurs on the back of the hands, fingers, edges of the feet, etc. (Figure 8-3), but can also occur in other parts of the body. Those that occur around the nail are called periungual warts, and those that occur on the nail bed are called subungual warts. Warts that appear as elongated protrusions with keratinized tops are called filiform warts, and they tend to occur on the neck and eyelids. Those with uneven finger-like protrusions on the surface of the wart are called finger-like warts, and they commonly occur on the scalp and between the toes.

[Symptoms and Symptoms> 1. Generally no conscious symptoms, occasionally tenderness; 2. Skin lesions range from pin tip to pea size, semicircular or polygonal papules, with rough surface and obvious keratinization. When touched, Slightly hard, grayish-yellow, dirty brown or normal skin color, papillary-like proliferation, and the surface is mostly stamen or spiny; 3. Commonly found on fingers, back of hands, nail edges and feet.