Black bump on my cat's nose?

Our cat Mona is abouot 16-17 years old, we've had her for 11 years now. She's a European Shorthair. We recently found out that she lost almost all of her hearing, but apart from that, she seems to be a very healthy, happy, playful and energetic cat. Despite her age she doesn't seem to have changed at all in all the years we've had her.

I'm starting to worry over a small bump she has on the bridge of her nose. It's been there for a long time now and it doesn't ooze anything, it's not red or inflamed and it doesn't seem to be causing her any discomfort. Recently it's turned very dark in color though and I'm scared it might be an ulcer. She's a housecat and we have no other pets so it's not a  bite or a sting from anything.

I know I should probably take her to the vet anyway but I don't want to inflict any unnecessary stress on her since she isn't used to leaving the house and being in unfamiliar surroundings. What do you guys think the bump could be?

I added a few pictures of her where the bump is visible:

Where is the bump? It just looks like a multi-pigmented cat nose to me.

That greyish area above the brown half of her nose. It could be, but I'm pretty sure it hasn't always been that color. 

Oh, I see. It's a slightly lighter shade of 50 than the rest of her face. It doesn't look bad to me, but I'm sure it looks different in person and I don't know what the cat used to look like. Keep an eye on the shape, color and texture of it. If it changes, go to the vet immediately. I'm pretty sure cats can get skin cancer, but it's probably not that. Good luck!

Thanks! Yeah I'll definitely keep an eye on it, she seems fine in general though so it's probably nothing bad (I hope).

Also, she's unbelievably adorable! I'm in love with the first photo and want a poster of it. XD

Thanks! her facial expressions are hilarious sometimes haha