You can use chloramphenicol ~

Generally, cats can't open their eyes and have pus. Female cats lick their eyes because saliva is bactericidal. But if there is no mother cat at home, use a cotton swab or cotton ball, then dip it in warm water or normal temperature water (tap water, clean), or directly dip it in chloramphenicol and gently wipe the pus on its eyes. Then look for small cracks, then drop chloramphenicol and put it in your eyes. Twice a day, three times. It will be all right soon.

Anti-inflammatory drugs such as chlortetracycline eye ointment can also be used.

I hope your kitten will recover soon ~