I would certainly take it serious and try to find out what the root is of this thought.
At the same time I would him know hoe precious and what a special and beautiful is to you.
Maybe also organise playdates so he get’s to experience the value of friendships

My heart goes out to you and your gorgeous son. My gut feeling is that it is coming from school. You might want to make an appointment with his teacher if it continues in the new school year. If u are a religious family, could it come from the concept of “sin” that he hears about at church or at a Christian school? Maybe during the school holidays, you could take him on a few special outings just you and him to reassure him how special he is. I wish you every and your family all the best. If it gets very serious, u may have to consider talking to professionals.

Ask him why he thinks that; then you can address it specifically.

i too would try to get to the bottom of where it came from so you can help understanding the root cause.

At 7 in my opinion someone has been telling him his a bad boy maybe ask his teacher how he has been at school lately? Her reply should tell you if it is her saying it or not

My nephew went through this around the same age, and after trying to talk to him and figure out what was making him feel that way, they made the decision to take him to a professional. He opened up to them and he was suffering really bad anxiety. After getting help and learning ways to handle his feelings and emotions he has been so much better now that he knows these tools to cope. Good luck, I hope your son is ok

This is a hard one and hopefully you will get to the bottom of it. If not home maybe from media, school or friends. Children can get weird ideas at times or misunderstand what has been said. One of my lot was telling people at school he had Aids, this was in the 90’s , he teacher rang me up. He had seen something on TV and thought his scar on his arm where their had taken a skin graft when he was very young was a sign of it. So I think you just need a quiet time and have a talk about why he thinks this.

This would worry me too. Maybe ask him what makes him think that he is bad – what has he done etc. that substantiates his statement. Point out specific times when he is being good/positive. Can you talk with his teacher? Best of luck in instilling a positive self worth ????