Hello,
I am sorry to hear about your broken leg.
With a casted limb (in your case, lower leg), it important to feel the toes making sure they are warm and have good sensation. Too much swelling in the leg can cut off blood flow to and from the leg and compress nerves to the foot.
Generally, the limb will hurt more when you stand. Blood is pooling in the limb. It pools because the lower leg muscles can not contract and work to pump the blood back up the leg. So stopping and elevating the leg periodically is important.
Pain is the body's natural way of protecting the limb from too much swelling.
Nevertheless, it is important to call the orthopedist and let them know what is happening, they may need to check and/or change the cast.
Let us know how things go and if we can answer any more questions.