Help! Parakeet's nails accidentally trimmed too short!?

Cornstarch, if you have any, but flour will probably do if that's all you have. It should have stopped bleeding heavily by now, if it hasn't then you probably need to contact a vet, keep checking up on it for now though. You can buy styptic pencils or powder from a vet, I know that's difficult to get hold of straight away but it might be an idea to buy some and keep it on hand for if it happens again. Cutting nails/claws of animals can be really tricky! I hope your parakeet is okay.