I have a small lump under the knuckle of my little finger from hitting a post. my hand & wrist hurt, but i have movement. could it still be broken?

Yes: The only way to know for sure is an X-ray .

Hand fracture in the: 5th metacarpal knuckle or neck is often called a boxer's fracture ( but real boxers know better) pain, swelling decreased motion are all signs that a fracture may be present. An evaluation and xrays are the next step. Most 5th mc neck fractures heal uneventfully but proper care makes it go a lot easier. Treatment specifics depend upon exam and xray finding details, .These fractures can be a "bump