You should go see your primary care doctor
or a podiatrist
for help with this issue. There are a few different causes of the type of pain you are experiencing, and they will be able to help you figure out what to do next.
The most common cause of pain in the sole of the foot is something called plantar fasciitis, which is an inflammation of the connective tissue in the sole of the foot just in front of the heel bone. This is typically not caused by an injury
but, rather, from over use or strain, say from wearing shoes without good arch support or from standing on your feet all day long.
Other common causes of foot pain in this location include bone spurs on the heel bone and flat arches.
All three causes of foot pain are generally treated in the same way. This involves, first, switching over completely to good shoes with supportive arches. Additionally, stretching exercises to stretch out the Achilles tendon and strengthen the muscles in the arch of the foot are important. Finally taking a good anti inflammatory medication like ibuprofen will help with immediate pain relief.
See your doctor as soon as you can to start your treatment!