I have a bad cold and am afraid I may not be able to breathe well on Yom Kippur. Can I put in nose drops on Yom Kippur?
Taking nose drops on Yom Kippur would be the same halachos as taking them on Shabbos. If you have temperature, and are considered sick, then it is permitted since then you are considered a choleh, additionally, if you feel that bad that you would have to stop what you are doing and have to get into bed, or if it feels like your whole body is weak from the pain, then you would be considered a choleh and it can be taken. However, if you are not feeling so bad, then the same way it shouldn’t be taken on Shabbos, it shouldn’t be taken on Yom Kippur.
H-shem should send you a refuah shleima, and you should feel better before Yom Kippur.
O:CH 328-1, Orchos Shabbos 20-145.