Hi zhitxng, welcome to the Forums, but I'm sorry that your little one seems to have had an accident of some sort
Unfortunately I am not an avian vet, nobody here is. However, it does look from the photos as though there might be some sharp edges left on his beak as a result of the chip, and that gap may indeed be making it difficult to eat. He may also be experiencing pain or discomfort with his beak, and that might also be a factor in stopping him eating as well. That being the case, I would suggest that you take him to a certified avian veterinarian for assessment, they should be able to correct the sharp edges and make it easier for him to eat. Understanding that there may be limitations on avian vet availability and that I am not exactly sure where you are located, the following link may help you to find one if you are not already familiar with one...
After a suggestion by a member, @Abu Colo, the Mod Team decided to create a list of veterinarians around the world who see birds. This was something we had discussed a few years ago, but the task seemed so large that we didn't get very far. However, the need is there and we decided that the time...
www.parrotforums.com
Thank you for joining and reaching out for help, and I hope your beautiful little one will be ok!
Right, beak trimming will help and patching is possible too. In time, it will also grow back. Please show us a photo then, so that we can rejoice with his new beautiful beak.
For now, he may get hungry and have difficulty eating hard pellet, soak them in water to make it mushy-easy to eat. Does he eat other soft food such as banana apple sauce
ripe papaya, ripe mango
Boiled pumpkin, cooked rice
Unsalted Soft scramble egg
Introduction of new food depends mostly on familiarity and trust. For instance, leave unpeeled mango in his cage for a few days. Your buddy will get less afraid of the new smell. Then cut in small size so it is less intimidating. As for how to offer new food, this thread has detailed information.