slight darkness under whiskers near nose

I brought a stray 7 mos old cat home but he got a bit upset in his carrier. brought him home monday and noticed a slight darkness under his whisker near side of nose today.     i feel its bruising.    otherwise he's the happiest loving cat i have ever had. he craves affection and love and is just so happy to have a home after not having one for 2 months or so.  plus having a non breakable flea collar or phermone collar on him and a very tight thick braided rope collar is  something you would see on a dog or a babys wrist which was not breakaway i can see why he is so happy. Do or can cats bruise?

Is there anyway you can upload a photo? I don't think I could even begin to guess without being able to look myself.
Only word of advice I can give is I would get rid of the flea collar if I were you. When I put one on my cat, he lost all the fur around his neck. Some of them can be really toxic.

Some came off. But now its a bit dark near the opening of the nose. I have a feeling he hurt it in the carrier as it was not there before. Also the poor cat was outside for over a month with no one to talk to etc except me when I went to see him so perhaps his juices got going. Will give him a while to settle down and perhaps bring him to the vet but they will only give him a rabies again. I'm sure this cat has had rabies.  it had two collars on him. one either a phermone collar or flea it was purple and not breakaway and a tight double braided rope collar with an unbreakable latch which was tight. he still itches his neck a bit without the collars and had a flea or two. the cat is only about 7 or 8 mos. he's sleeping in my lap now.