You need to capture him immediately and get him to a veterinarian. The grits or cream of wheat would be the wrong thing to feed him as it may cause him to bloat.

The swan will die if he does not get veterinary medical care with supportive care and antibiotics. He may have fishing line or a hook in his mouth which will keep digging into the soft tissue. Even if it is not fishing material, a foreign object may still be embedded and causing an irritation resulting in an infection which will ultimately kill him no matter how much he is drinking or eating. If you can get him close to you, you will be able to capture him, but you may only have one chance because he will get smart and avoid you if you fail the first time. If you are hesitant in capturing him, contact a local wildlife rehabilitator or similar wildlife rescuer that is comfortable in helping you capture him. The Regal Swan