Toddler cold remedies ?

My son is 2 and just contracted his first cold. His nose is running like a faucet, but he can’t breathe out of it (he can still breathe fine out of his mouth) so he’s not sleeping well. I tried a humidifier, but ended up with water dumped out all over his bedroom floor because it was too interesting for him to resist and there’s no where I can put it in his room where he can’t reach it, so that’s out of the question. I’ve been giving him 2 hot showers a day to clear up his nose, and it helps a little. Anything else that can help? Is there any medicine he’s allowed to take?