No, that is not normal. However, if you have recently increased your activity level, and have the leg hanging down quite a bit, you may have developed some swelling within the limits of the cast. Since the leg is in a cast, it is essentially impossible for the limb to swell so much that the wound would dehisce (come apart). However, extreme swelling can cause other problems, such as compartment syndrome.
Unless there is a reason for the ankle to feel worse (ie using it more, not elevating it as much as you should, accidental trauma such as stepping down on the foot when you didn't mean to, etc), increasing pain and swelling should be evaluated by your surgeon. The limb should feel progressively better as time goes by.
You might try keeping the ankle elevated as much as you can and put some ice on it. (Yes, the cold actually does get down to the skin, through the cast.) If this takes care of the symptoms, then you know how to take care of it. But, if this does not help, or your symptoms get worse, you should call your surgeon and ask if he/she needs to see you. If you call before trying the elevation, he/she will probably tell you to elevate it and call if it doesn't help. So, this way you are one step ahead of the curve.