It's perfectly safe to wash your finished cross stitch. First check the ends are all secured on the back of your stitching. Then fill a bowl with warm water and add a little detergent or needlework shampoo. Immerse your stitching and swill it around. Rinse well in cold water but do not wring it out. Then press your damp stitching on top of a fluffy towel with the iron on a medium setting. Push the point of the iron into the back of the stitches to make them stand out.