Melody23, Be sure to call the medical centre prior to the examination and find out. Just be honest and say you ahve hurt your foot.
When you see the doctor, he will test your strength in your arms, push, pulling. Squatting, reaching, you will be poked and prodded. I can't really see if a sore foot would affect you, but if your foot is seriously hurt, make sure you tell him first hand so he can diagnose that you'll be good as gold by the time you get your job.
I had the flu at the time of my medical, so I was afraid that could affect my results. But i hadnt taken any codeine at the time and i told the medical centre prior to my examinations AND on the day as well. having the flu affected my breath-holding exam in the medical, but was given lee-way because i wasnt feeling well.
Best of luck, Don't stress