I'm sorry to hear that you are having such discomfort in your foot. I recommend that you go to see your primary care doctor
about this issue, especially since the pain has been going on for a week now and is not improving.
There are several different things that could be going on and your doctor will be able to examine your foot and help you figure things out. Even though you don't recall injuring your foot, do make sure to tell your doctor about the kinds of physical activity (such as running) that you are have done, as a sprain of the foot or (much less likely) a small stress fracture
would be possible causes of your pain.
Another very common cause of foot pain
is something called plantar fasciitis, which is an inflammation of the connective tissue on the bottom of the foot. This condition can occur in the absence of any vigorous physical activity or injury, and it causes significant pain on the bottom of the foot in front of the heel bone.
After a physical exam, your doctor will be able to tell you if you need x rays, and what medications you can take for the pain.