If you're getting lots of pain, and can't walk properly, I put it to you that you won't be wasting anyone's time by going to see your GP. It may be a sprain, or some such, that will mend with time, or you may have done something that - if it's not seen to - will get worse and perhaps become a permanent issue. I don't personally think anyone on here can diagnose the problem because, by and large, we're not healthcare professionals and in any event we can't conduct an examination of your foot.
So - I urge you to make an appointment to see your GP or, if you really aren't able to do that (and I know what a pain it can be to try and do so) go to the nearest A&E and insist on sitting there until someone will see you.
I hope it's something completely trivial that will sort itself out, but don't take any chances.....