Betta Fish: Hole in head or injury?

First time fish owner, noticed this on my boy Sprinkles this morning. Yes he is normally this bad at getting his food, no worries there. Is this an injury or jole in the head, and how do i treat it?

Details: he's in a 10 gal fully bioactive tank, sharing it with some snails of various species and some amano shrimp. No other fish in the tank. I've had him for several months now and he hasn't shown any problems before

Thanks in advance for any advice