If you hit your elbow at just the right angle you are striking the ulnar nerve which then compresses against bone, causing an electrical sensation in the area and frequently down to the hand. The elbow is not typically an area that has a lot of fat cushion to protect the nerve, making it an easy target for some.
Before the ulnar nerve reaches the elbow, it runs from the neck down through tissue and along the humerus bone which is pronounced the same as humorous (aka funny) and may be where the ulnar nerve got its nickname. Generally, pain induced from striking your funny bone resolves quickly. There are some things that you can do to minimize the chance of irritating your ulnar nerve, namely avoid leaning on your elbows, limit activities that require keeping your elbows bent for extended periods of time, and sleeping with your arms at your sides.
If funny bone pain persists you may be experiencing cubital tunnel syndrome and is a more serious condition that requires aggressive intervention to avoid muscle weakness in the forearm and hand. Talk to your ASAP provider about treatment options. We will do our best to help you start laughing and see the funny side of things again as soon as possible.