Lost Pickaxe, how i get a new one!?

You can make one if you have resources & craft stations but if you are brand new, if you die you spawn with another pickaxe and woodaxe (but will drop anything else in inventory on your corpse). So either find someplace "safe" too die, maybe fly up in air with F2 then toggle F2 again and deliberately fall to your death. Or die of hunger/thirst. Or if you have nothing to lose, punch a bear or jump down a cave.

You can actually get quite a collection of pickaxes/woodaxes by dying repeatedly, though any more than one is not much use.

You can also make a new one by typing item pickaxe 1 into the console. You can open the console by typing the ^ or ° key.