Call the surgeon right away and report your symptoms to him. I don't know when you had your last follow-up visit with him, since the surgery, but he needs to know of the extreme swelling of your foot and ankle. Continue to keep it elevated, preferably while lying down so it can be propped on a pillow making your foot higher than heart level. Please try to stay off of it for the rest of today, and keep it up. The doctor will want to take an xray. You may have been up on your feet for too long and fluid has seeped into the tissues in the area creating the swelling and pressure which is giving you severe pain. However, medical exam is needed to be sure that there is no further injury.
I hope all will be well with you!
Feel free to let me know.