Might have been the cream, if you use it. Or something in the coffee, could it have been mold? If it isn't in a busy place, then it could be caused by nearly anything. Do keep a close check on it and should it keep spreading, then do go to the doctor. Something that severe should not be happening.
Write down the name and address of the little place you got this coffee and sweets.
You might want to check with the local health department, if they have many (don't know the number that will get them moving) complaints about a place they will investigate to see what was causing the trouble.