My kindergartener is afraid of a first grader because of one situation that happened over a month ago. My son was kicked because he growled at the other kid. Now my son is afraid to go to school because he thinks the kid is "looking for him" and will hurt him again. He has very little contact with the kid; he sees him at lunch when he leaves the cafeteria and the other kid enters. His anxiety is getting worse and I don't know what to do.
This sounds like a difficult situation. We read a ton about bullying nowadays and our tendency is always to ask our children, "Is anything going on at school?" My sense is that you have already assessed the bullying situation and have come to the conclusion that he is not in danger. Nevertheless, the danger seems real to your son, so he feels anxious and scared.
Keep checking in and reminding him that his safety and comfort at school are important to you and his teachers. Give him a chance to explain why he still feels worried. Point out that sometimes when scary things happen (like getting kicked), our brain can trick us into thinking that the scary thing is going to happen again, even when it might not. It’s our brain sending us a "false alarm." Also point out that the other child has not actually been looking for him, even though it may so to your son. A school psychologist or social worker might be a great resource to reinforce your message to your son, too.
If these fears and anxieties persist and seem to impact your son’s ability to go to school and have fun, or if his sleep, appetite, or interests are affected, call a mental health professional who can assess for anxiety disorders and offer treatment recommendations.