What could cause the bottom of my foot to hurt?

The bottom of my foot hurts near the top by the toes. It hurts to walk or put pressure on it. What could be causing this, I don't really wear shoes since I am a stay at home mom, its usually slippers or socks, or bare feet at home. If i go out i usually wear my Ugg boots in the winter and flip flops in the summer. So i know my shoes aren't to tight, and I'm not always in high heels.... It's been day 3 of this and it isn't going away!! So again anyone have any ideas as to what could be causing this, and how to treat it?