Have you tried cold packs on it? Is it discolored?

If your hand is showing color changes, I'd get evaluated for RSD (reflex sympathetic dystrophy). Some people get RSD in the arm from needle sticks in the elbow depression.

One thing showing up in studies, about RSD and wrist/foot trauma is using Vit C to reduce risk of RSD occuring. 500mg to 1000mg a day was used in Britain in several studies. Time period is 50 days or so.

If you think RSD is occurring you best not use cold treatments.

What kind of IV was used may I ask? Some dyes for visualization can leak out of a vein to nearby tissues and cause irritation as well. That happened to me with IVP dye. It also resulted in my tissue making antibodies to it, and I became allergic to it and the next time I had the test, I had a severe allergic reaction. So keep that in mind too.

Typically it can hurt in the hand. I have small veins too, and sometimes I have pain in my hand for a few days after giving blood samples.

This is our RSD forum:
http://neurotalk.psychcentral.com/forum21.html

It is good to know if this is happening to you, so you can get intervention, to prevent RSD spread. Sometimes it can spread and be much worse. So I'd ask the folks over there for advice too.