Hi
@Traveler17
Can you post some photos?
It sounds like your rooster has Canker (Trichomoniasis). A vet can confirm what he has and hopefully prescribe the correct medication for you.
Some people don't have a vet, so do treat at home. Metronidazole (FishZole, Flagyl) can be used to treat Canker. Dosage is 250mg divided into 2 dosages given 12 hours apart - give daily for 5days. FishZole is found online or if you have a local fish store you may be able to find it there.
Canker is a protazoan infection, smells bad and is highly infectious/contagious. Separate your rooster and clean/sanitize all your water and feed stations that your other chickens are using.
Some people also recommend using Acidified Copper Sulfate in the drinking water to help prevent infection - if you feel that you need to administer that to the rest of your flock, it may not be a bad idea. Put 1/4tsp Acidified Copper Sulfate in 1 gallon of drinking water for 3days a month. (Use only a plastic water container).
This is what Canker can look like -- again, if you have a vet that can assist you to make sure you have the correct diagnosis, that would be best.