Forehead Bump

My son is 5 weeks old and has this squishy bump on his forehead. It does not seem to bother him when we gently touch it. It appears and then disappears and his forehead is flat again. It is more pronounced when he is crying but at times looks like this when relaxed. Anyone know what this could be? I was going to bring him in the 1st day I noticed it (Wednesday) but then it went away. Since then it is random when it will come back/go away- be more prominent/less noticeable.