Yes, you can just go ahead and temper the blade. Be sure to use a thermometer in your toaster oven instead of going by the setting on the dial. You might want to try a vegetable oil in the future. Stuff like engine oils and transmission fluids sometimes have things in them that would don't want to put into the air you're breathing by sticking red hot steel into it. One risk that you run by not tempering right after you quench is that you can have cracking just from the stress in the steel crystals.
Doug