Are we talking about a tiny fraction of an inch.. or a few threads different? or something larger..
One of the things that can cause you to have slightly differing cuts is that fabrics are different.. or sometimes they fabric isn't truely square.. so a perfectly cut block might lean a bit one way or the other..
Also once a block is cut we pick it up move it here and there.. perhaps press it.. Fabric is not stable.. it can and does move.. some more than others.. wood is stable.. you cut one inch.. you have one inch.. fabric gives, so it can be a tiny smig off.. .
I would say if it's only a tiny bit.. a few threads.. or the lean of the block.. don't worry.. when you sew and press and square up your blocks, all will work out just fine! Remember quilting is FUN, and RELAXING, not something to frustrate and irritate you..