And that is a funny way to spell humorous.
Also, it is an odd feeling, not really pain, but strange or peculiar, or as some people put it, a “funny” feeling.
Besides, your funny bone is even funnier because it isn’t a bone at all that responds. It is the ulnar nerve. Unlike most heavy-duty large nerves, the ulnar nerve is almost completely exposed. The ulnar nerve runs in a bony groove called the “cubital tunnel” through the elbow, where all that stands between that hard thing you bumped and the nerve is an thin layer of fat and skin.
More about how it works here.