I Have Small Lump, Which Is Sore, On The Ball

I have small lump, which is sore, on the ball of my foot. It happened over night. I shouldnt really say lump because it is not sticking out- but if you rub the foot you can feel the knot. But when I walk I can for sure feel it- I had something like this in my right foot a few months back and went a way within 24 hours. I am a teacher and on my feet all day. But I do all I can to wear proper supportive shoes.