Puffer help

My puffer has been with me for a little over a month. He is in a 125 tank with the following
pH 8.2
Ammonia is 0
Nitrate is 0
Nitrite is 0
Temp is 78
Salt is 1.021

Tank mates are
Coral beauty
Fox face lo
Two mocha clowns
Two clarkia clowns
1 dragon net
1red head fairy wrasse
1 blue head hairy wrasse
One vrolik wrasse
One timing tang
1 latticed butterfly

He eats well and his favorite food is scallops. I noticed this sore on top of his mouth this morning was wasn't sure what to do. He is about 4 inches long. He is a Narrow Lined ouffer

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