I’ve general and local many times in my life – my biggest suggestion is to make sure he is drinking plenty of fluids. This should have been part of your going home instructions. The anethesia needs to be flushed out of his system and many times men forget to drink 8 glasses a day (even hard for women too).
The actual pain from the incision and the procedure itself could also be tiring him out. Think about pain from a throbbing headache but place it in your hand – not the easy thing to deal with especially the pain relievers can make you lethargic.
I think it’s a combination of factors here – If the incision does not appear to be healing properly before his next visit for after care – please contact the doctor because staff infection should not be ignored.