If he did say so

[Maybo]

Carmine continued to stare at the old man's bedroom from the yard. It had been nothing but a charred cave two weeks ago. Now it was looking mighty fine if he did say so himself.

Source: The Exorcist's House by Nick Roberts

What does “if he did say so himself” mean?
Carmine was one of the construction crew to renew the house he was staring at.

 

[Tarheel]

It's a common expression. It's like you're apologizing for bragging about yourself. (See below.)

I did a really good job if I do say so myself.

Instead of somebody else saying it, he's saying it himself.