Hello. Thanks for asking from HCM. I can understand your concern. It seems that you had mild head injury on the back of your head. The swelling at injury site is due to the collection of blood in scalp tissue and edema of that area. It will disappear on its own in few days. You can apply ice over it to relieve pain and fasten its disappearance. There is no problem in sleeping after mild head injury like yours. Sleep will not cause any deterioration of your injury. However during supine posture, pressure over swelling can cause pain and disturbance in sleep. So try to sleep on either side on turn not straight. Alarming signs which you and your mother can look for are vomiting, persistent headache not relieved by pain killers, loss of consciousness, ear/nose/throat bleed, fits, memory disturbance, onset of new focal deficit. If you notice any of above signs, consult ER as soon as possible. Thanks. Hope it will help you. Take care.