No one wants it, yet it's the body's way of getting your attention when something is wrong. You're probably sufficiently in tune with your body to know when the pain is just a bother, perhaps the result of moving furniture a day or two before or eating that third enchilada.
Wrist Blood Pressure Monitors use the radial artery to measure blood pressure instead of the more commonly used brachial artery. The key is to place the monitor on your wrist properly, just above the wrist bone and then to hold your wrist up level with or above your heart.
There are also two arteries (radial and ulnar) that supply blood to your hand. You can feel these on the palm-side of your wrist. The radial artery (nearer your thumb) is often felt to take your pulse. The ulnar artery on the opposite side of your wrist is much more difficult to feel.