I had a vintage quilt that was discovered and "too nasty" to play well with the others in the stack so I did wash that one. Most recommend the bathtub method but I filled my washer and put the quilt in that to soak. That way I could turn it to spin and get more of the water/soap out of it than with the tub. If all that has you concerned is that crease, I would simply lay it out or even hang it for awhile to see if that crease won't soften. This is why it is recommended to refold quilts every so often but most of us don't. Time and attention slip away.