i think you can't do anything with it, i have a lot too :(

Maybe Duo team do something about that . Soon:)

you can buy some stuff like bonus skills and streak freeze in the lingot store just click on the lingot sign on the blue bar and you are at the store

Give them away to discussions and comments you think pushes the community in the right direction. Reward people. Here, enjoy a Lingot.....didn't that feel good just for one second? And push for more possibilities in the DL store.