Question
I was doing a little pruning of a path leading to a creek on our property when I got stuck in the wrist area with a thorn from a honey locust tree.It didn't hurt at the time too much..but a couple of hours later it felt like a bruise..and a few hours later it felt like a broken bone and was swelled pretty good ...How long will this last...its very painful?

Answer
There is not really a poison in the thorn but being stuck by any number of thorns (rose. locust etc.)they all seem to cause a medical problem. More then likely the dirt and dust gets into the wound and causes infection. Or when it is pulled out a small bit remains and festers.
from Penn State Robert Nuss, professor of ornamental horticulture

"Thorny plants. The most common plant-related injuries are caused by thorns. "Most people don't seek medical help after getting stuck by a thorn," Nuss says. "But implanted thorns, needles or spines can cause infections or other medical problems."

Nuss says thorns embedded near joints can cause chronic arthritis. Thorns embedded near bones can mimic a bone tumor. Thorny plants that can cause painful injuries include roses, black locust and honeylocust trees and blackberry bushes."  

We can rule out toxicology here, as Honey Locusts show no signs of toxicity, and only the seeds of the Black Locust are dangerous.
There is also the chance of an infection.

Now I guess that anything foreign to the body could be classified as a "poison" such as dirt or dust  on the thorn or the thorn itself but the plant itself is not toxic.  

you have a piece of the thorn still in your finger, and it's acting as an irritant. There is also the chance of an infection.

If it weren't near a joint  treat the infection, and see if it dissolves or expresses out, as splinters usually do. But near a joint, there's the potential for damaging the joint.

Try soaking the hand in warm with Epsom salt dissolved in it for about 20-30 minutes, not only to clean it but also to soften the skin. Then, with a sterilized needle, tweezers, alcohol (not for the wound -- to disinfect the equipment and the skin before you explore) and a magnifying glass, see if you can find the entry channel, and follow it down. Don't go overboard and hack a gaping crater in your finger -- the ideal here is to be extremely gentle and also persistent. If you can find and remove the splinter, hit the wound with hydrogen peroxide, bandage, and watch it heal.

If you can't find the thorn, or can't get all of it out, an X-ray and a man with a scalpel (and a license to practice medicine) is called for.

The concern here is that, if the shard works its way into the joint, you may wind up having problems with that joint for some time to come. IF it continues go see a doctor.