sixline has sore on side

[blackdog]

Here is a rather blurry shot of my sixline I took this afternoon. Just in the last few hours he has developed this sore on his side.

The photo is blurry, but the depiction of the sore is accurate: There is a spot where his coloration is brighter, particularly the orange. Toward the middle of that is a smaller area that is grayish. I do not see any stringyness, fuzz, or white spots.
His behavior is fairly normal, although he may be somewhat more active than normal. Just in the last couple days, he and the royal gramma have been having a little turf war over a cave that the gramma has claimed for himself. Sixto swims up to him and the gramma gapes his mouth threateningly. I haven't seen them actually make contact with one another.
One other question about Sixto. In the last week or so I have noticed that there are what appear to be small red pinpoints around his mouth. Is that just part of his coloration? I'm hoping so. I hadn't noticed it before, but his colors in general have been growing more vibrant over the last couple weeks. I have had him for about 2 months.

 

[beth]

Where is the sore? That spot at the base of the tail? Is it an open wound?

 

[blackdog]

You can see the sore in the photo on his left side. It's an area about 1/16" in size that's kind of raw, sort of like road rash. I didn't know if it could just be from scraping against something in the tank, or if the gramma gave him a good nip (on the side?), or if it's the start of some infection that I could treat.
The sun is coming up in the tank in about ten minutes. I'll check on him then and report...

 

[blackdog]

The lights are still kind of low in the tank, and he won't hold still, but the sore doesn't appear to have changed.
He seems to be twitching side to side every now and then. But he's not rubbing against anything.