Take the covers off and oil again. Slowly turn the hand wheel by hand until it's turning freely. Oil all areas where moving metal meets metal. I use Tri-Flow for this purpose. If you see rust, you can use a copper scrubber gently or use a paintbrush dipped in a bit of evapo-rust. Usually you only use lubricating grease in a motor. I've also used a thin artist paint brush to get oil into little crevices around the needle bar which helps to unfreeze it.