What Causes Smelly And Wet Circle Under Breast?

Hi.. two weeks ago my husband, son and i went to the park.. as i was sitting down i started complaining about a sudden pain under my breast.. when i went home.. i noticed two little circles. I then concluded something had bitten me.. It has been away now for a week.. and yesterday i woke up and found a huge big RED circle under my breast.. not sure if it has anything to do what happeend in the park.. its smelly and wet.. do you have any idea what it might be?