Removing a 'baked in' rice (carbohydrate) stain

I live in Asia and we remove our shoes in our houses.

I accidentally stepped onto some rice (another Asian reference) in my socked feet, and it left quite a sticky white residue on my black socks. I quickly tried to wash it away with some water, but it was too sticky to be removed. I left there thinking it would be easy to wash away.

Unfortunately, I forgotten all about this rice stain and sent it for normal wash and dry in the machine.

Now there’s this ‘cooked in’ white stain on my black cotton socks. I can’t scratch it off and it remains there no matter how much I wash it.

Could anyone help me with some ideas to remove this stain? The only thing I can think of now is to buy some permanent ink and dye it back black!

Or you could just buy another pair of socks. The cost of the fix may be more than the cost to replace. I would chalk it up to experience and move on.