I have a 7.5 y/o apbt/american bulldog. Recently he has gotten a dark spot in a colored spot over his ribs. It's oblong in shape for about 2 weeks and as of today foul in oder. I have given him a bath today and right after is when I noticed that something was not right. I smelled all over his back and it only smells on the discolored section on his side.
I am going to take him to the vet but they are closed until Monday so I am just looking for some suggestions on what it may be.
<3 thank you so much!

Moved to dogs

You didn't specify what the discoloration looked like...
Is is wet/dry? Is it the skin or just the fur?

It could be a 'hot spot'
The most common breed to get them are shih tzus and other long coated breeds but it is possible for other breeds to get them.
Some dogs never have them until they are older, others have them frequently their whole life.

Another possibility would be skin mites.
Usually when they are localised they gather around the head but once again, anything is possible.

Another problem could be allergies.
If he is over 7 years old the this is unlikely unless you have changed his food or planted new trees etc.

Please come back out let us know the outcome after he has gone to the vet.