Ulnar nerve
The ulnar nerve innervates the medial 1.5 digits on the palmar surface of the hand, and 2.5 digits on the dorsal side. So, this is the nerve responsible for innervating the tip of the little finger. The radial nerve innervates the dorsal side of the lateral 2.5 digits, but does not innervate the tips of these fingers. The median nerve, which innervates the palmar side of the lateral 3.5 digits, also innervates the fingertips of these 3.5 fingers. The musculocutaneous nerve does not provide cutaneous innervation to the skin, but its branch, the lateral antebrachial cutaneous nerve, innervates the lateral skin of the forearm. The medial antebrachial cutaneous nerve innervates the medial skin of the forearm - this nerve is a direct branch of the medial cord of the brachial plexus.