my bf has something attached to him and it marked a sigil on his chest

i’m not really sure if it’s the right place to write this, but my (F23) bf ((M26) had something attached to him from when he was 2. he claims it’s a female and calls her ‘dream visitor’, as she comes in his dreams. the way he describes the dreams, they are short and spooky, but funny part is my bf has gotten so used to it that he doesn’t get scared anymore. i never got any bad feeling about her and my bf believes his dream visitor has protected him from bad circumstances. so last weekend my bf was at my place and we took a long nap at noon. he saw her in his dream standing right before his feet, staring at him. he remembers her face vaguely and she was wearing something full black. then she did a hand gesture in her chest and right after that my bf noticed a red glowing sigil in his chest for few seconds. the sigil seemed like alphabetical. then she vanished and as always, my bf was paralyzed in his sleep and moved his body with all his strength to wake up. when he mentioned the sigil part, something in me didn’t like it. i’m not saying anything bad about her. but sigil? i am worried. can anyone have any theory about this? thank you for reading.