I may have a hand fracture. How do I tell? Is treatment necessary?

I hit my hand pretty hard yesterday and am feeling extreme sensitivity from the site that received the brunt of it all. It is along the outside of my left hand, along the side right above the wrist and the bottom most knuckle of my pinky finger. There is some bruising, but it is minimal and mostly beneath the surface. I have fairly good mobility, but the specific spots are very sensitive to certain movements and extremely pained when poked or prodded. There is also some sensitivity around lifting heavy objects or opening heavy doors, anything that applies any pressure to those points. Sometimes the pain will subtly shoot up my forearm. Is it possible that I have a hairline fracture or more likely that I simply have very deep bruising? Should I worry about treatment or x-rays? Or will it heal relatively well on its own without any help. Thanks!