As others have said - washing it at this point will accomplish nothing positive.
However - if - for some reason it is necessary to wash a quilt top because it got something unpleasant on it - swish it in a tub or sink - do not agitate it in a machine - run water through it or something - rinse gently - roll out in towels - dry on a rack or on towels on a floor -
agitate as little as possible - there will still be annoyng fraying of the pieces, but it won't be a disaster - assuming all the fabrics were washed BEFORE cutting -