What would a broken finger look like?

It depends: It might look disfigured (crooked), have a lump in it, hurt when pressed or used, and be hard to bend. It could also be bruised. On the other hand it may have some or none of these signs. If you are concerned, the only way to tell for sure is to do an xray. Tape the injured finger to the one next to it until you have the opportunity to get it xrayed.

Painful deformity : A broken finger can look normal or it can have a deformity. In either case, there is usually significant pain with movement. Bruising is also often seen with fractures.

That varies: Depending on the location and type of fracture.