Aww, poor guy. I'm so sorry you two are going through this but welcome to Fishlore. I hope we can help.
This is not meant to sound harsh, just... it is not the time to determine if this will be fatal or not, only to do your best to care for the fish in their current state. At this time he has a wound to be cared for and it is just too early to say whether things will get better, or worse. On one hand, I imagine things could get better, but on the other, a fish that is strong and healthy otherwise will not get stuck to an intake. So, I'm sorry to say that it sounds as if your fish was already weakened from something or another.
Okay, with the tough stuff out of the way, let's get on to what you can do. Keeping the water in pristine condition will go a long way to helping your guy heal as well as a big help in keeping infection at bay. So, water changes are your best friend right now.
It also wouldn't hurt to soak the fish's food in a fishy vitamin like Selcon. Many aquarists report that healing is hastened and much improved when feeding vitamins. It is also said that vitamins will boost immunity and this is key because the greatest problem your fish now faces is a bacterial infection.
Wounds will heal on their own with time and the best way for us to help is with super clean water and a very good diet. If your clown shows further signs of deterioration, I would suggest medicating him... which is best handled in a quarantine tank so you don't have to subject other life in your display to medication. I can help with meds but I do not think we are at that point just yet, and before recommending anything specific, it would be best to know more about your setup and the other critters you keep.