you could try some karvol on a tissue somewhere near the cot? (or put it on the sheets, if you're not worried if the karvol might stain!?) We've found a humidifier helps too. Otherwise just some baby vicks on his PJs/feet/chest? The saline nasal sprays can be helpful too (the non-medicated ones).
Unfortunately I think it's just a case of riding out the worst of it