All Of A Sudden My Right Ankle Begin Swelling My

all of a sudden my right ankle begin swelling my foot started hurting , i took some iburprophen , after about an hour it stopped hurting and was fine, i was walking fine and all no pain later on it suddenly started hurting again , more meds it off, when i awoke the next morning my foot was bruised on the inside, i did not hurt it in anyway that i know of , it was pain free tho until that evening and it started hurting again and i noticed even a bigger area that bruised , what could cause that .