Oh dear! You want to avoid washing the top in your washing machine as it will cause the pieces to fray and may create holes. Get a dust pan and scrape off as much dry mud off into the dustpan. If it doesn’t look too bad, quilt it, bind it and wash the quilt after spot treating the mud stains.
if it is still really bad after cleaning off the dry mud, try gentle wash in the bath tub. Let the water drain out and wait until most of the water has drained out, press extra water out and gently lift it into a laundry basket. If possible hang over a line to dry.
If your fabrics were not washed before making the top....do not get wet ....it may cause fabrics to bleed. Good luck!