What causes knot on your head underneath the scalp?

What are the types of embryo? How do you get rid of ingrown hair bumps that wont go away ive tried everything? What does body composition really mean? When people are in traumatic shock their blood pressure is high or low? Bleeding when i wipe 6 weeks pregnant? What happens if a girl doesn't get her period? Why would during menstruation blood come out dark red thick and almost like blood pudding? Which system includes skin nails and hair? What can a diabetic take for headaches? Bright red discharge prior to period? What causes a chest rash? What substance causes eyes nose ears and mouth to bleed upon death? What is frontal cortical atrophy as described with mild asymmetry at the level of the sylvan fissures? How disease develops? Can a wart spread if you put it in your mouth it is on finger? Why do sugary drinks make diarrhea worse? What to do if you inhale ammonia and bleach and your throat hurts? Is there a real cure for alopcia? How does acid effect the brain? If a person has an accident and sustains head injuries and as a result has trouble playing the piano and doing their gymnastic routines the part of the brain that was probably injured would be the?