What Causes Sharp Pain In The Middle Of Foot?

I woke up this morning with a sharp pain in the middle of my left foot, towards the part of the arch nearest my toes. It makes walking very painful. I examined my foot and saw a bruise a little smaller than the size of a dime. I touched the bruise and felt a small, round lump. I have never had this before that I know of. I am also experiencing a dull achy feeling either just under my right rib cage in my upper abdomen. It is just below or just under the rib cage. It is difficult to tell. When I stand up, the achy feeling seems to be below my rib cage. When I lie down, the achy feeling feels like it could be beneath my rib cage. I was treated for breast cancer 6 years ago, so of course I worry that cancer might be in my ribs.