Sudden pain in the ball of my foot

I am a fairly active 32 year old female, no prior foot problems, and regularly wear good quality athletic shoes. This afternoon I was power-washing my front porch, and upon finishing my work, came inside and removed my shoes. The ball of my left foot seemed very sore and upon examining it I noticed a slightly reddened tender spot about 2 inches below my 2nd and 3rd toes. There is slight swelling and the area is warm to the touch. I do not recall doing anything out of the ordinary that may have caused this. Any thoughts on what may be wrong would be greatly appreciated!