Conditions New guinea pig skin condition. Could it be ringworm? He's also making strange sounds.

Hello all!
I have some very sad news Harlow has passed away and I am very very sad about it, but she lived a good life and I'm trying to focus on the positives.
Like the fact that I recently got Dillon a future cage mate named Obi Wan (they are not living together until I properly introduce them and sort out this problem)
Last night I noticed Obi had crusty spots on his rear, I looked harder and found more flaky crusty spots on him I thought it might be ringworm so I put some ketoconazole 2% on the crusty spots and washed it off after five minutes. Now I'm not sure if this was the right thing to do. I should have asked for help first, but I panicked.

Obi is also making a strange noise from time to time, kinda like a whistling sound coming from his nose, it is very quiet and not noticeable unless you listen very hard I have listened to his chest and heard nothing he doesn't seem unwell and is running and popcorning but he also sneezes and has coughed once like he was choking on something should I be worried? I looked into his nose a few minutes ago and noticed what seemed to be an extra fold of skin in both his nostrils his nostrils also look rather small do you think that's why he's sneezing or do you think it is possible he is allergic to carefresh bedding? Obi doesn't have all the symptoms of a URI, he's eating, his breathing isn't labored, his eyes are very clear and bright, he is pooping a lot, but I will get that checked out.

Here are some pictures of Obi's skin. He also likes to chew on everything does this mean he's in pain? I have a link to a video but I dont know if I'm allowed to post it.


Thanks!