You most definitely need to go to have this checked out ASAP. They often cast a broken foot, depending on the type of break, might use a boot type cast. If the bones are out of alignment and it heals incorrectly, that is not good. If it is just a severe sprain, they also might put a rigid boot on it and put you on crutches. I think that either way, it needs to be checked out. The pain is your body telling you that something is wrong. You definitely need to listen to it. My hubby hurt his hand at work, some pain, not much swelling. He came home and I told him he should have it looked at, but her refused. Got up next day and his hand looked like a Mickey Mouse hand! Went to the doc and it was broken. He was in a cast for 6 weeks.
Good Luck!