Try to milk it. Probably that's not easy without real nipples, but maybe you can pull and squeeze the joystick and get the milk out. As soon as you manage to get all milk out of the :gp2x you can expect it to function normally again. But don't try too hard because there have been reports of a :gp2x turning into a gp32_console in similar cases (milk, cola, beer, it really doesn't matter what you spoil on it).
As an alternative, you may switch to other drinks as long as the :gp2x stays dedicated to milk.
Btw. writing in all caps generally is considered as SHOUTING!