Current amplifier for a solar panel
You can't break physics.

5V @ 5mA is 25mW. Power must remain constant (less converter efficiency), so (25mW*90%)/2A = 11.25mV (assuming an optimistic 90% efficiency). So if whatever you are trying to power is fine with about a hundredth of a volt (which I very much doubt), that's fine. Otherwise, you're gonna need a lot more solar panels.

Edit: regarding a current amplifier:

OP, you can build a current amplifier, but think about this carefully: what will you power the current amplifier with? If you power it with itself, that's not going to work for reasons mentioned above: you can't get more power from something. Or you power it with an external supply (a nearby outlet, say), which completely defeats the purpose of having the panel.