Put a piece of wood under the centre stand, and it will work again

If dousing the shock in WD40 helped, it's probably the bottom bearing of the shock absorber. Not so difficult to replace when you have a centre stand. Riding it til winter won't do too much harm; if the bearing has failed it'll give a lot of warning before it really gets dangerous.
Double check if the top and bottom bolts are tight on the shock absorber.