Nicrosil stores Investiture, and Stormlight is Investiture. Meaning you can, probably, store it in Nicrosil. If you were an Elsecaller, Lightweaver, or held the right Honorblade, you could use that Stormlight to Soulcast more Nicrosil, or other Allomantically viable metals. If you got the method down, you could theoretically Compound forever without needing to get more metals from an outside source.
Assuming, of course, that you can store Stormlight in Nicrosil.