it's a 1/4" - I don't think it's a big enough discrepancy to add a "border". To me, that screams "Look at me, this block is messed up"
When sewing the 2 blocks together, using the correctly sized block as your guide, place the smaller block on top of the larger block, centering it. When you sew your seam, use the larger block to sew 1/4". The smaller block will probably have only 1/8" inch seam.
When you turn your block over, you will never know.