Could sciatica be the reason my foot is sore?

Possibly. Sciatica is caused by an irritation or impingement of the sciatic nerve in the back of the thigh/buttock. It may cause symptoms all the way into the foot/toes. Consult a physician for a definite diagnosis.
Yes. Sciatica is the condion where the nerve is compressed in the lower back. The pain will than radiate down to the toes following the course of the nerve. This can lead to direct pain in your foot, or compensatory pain to your foot.
Possibly. Could also be Plantar Fasciitis. Would suggest seeing a sports & spine specialist, most physiatrists (PM&R doctor) should be able to figure this our for you.