When i have created them the size is 12x12 inch, so should edit them to allow bleed cut offs or leave it as is?
It depends on who will be doing the printing. Most photo labs that do 12x12 full bleed, do so by enlarging your JPG slightly to print past the 12x12 area, then they trim down to the 12x12 area, thus ensuring no white margins.
So yes, you must compensate for this by making sure nothing important is too close to the edge where it would get cut off.
On the other hand, if you send your order to be printed exactly 12x12 onto oversize paper where there will be white margins that you will trim off yourself, then you can leave your JPG as is.