Chemical burns produce the same damage to skin as thermal burns (from the sun or fire), just with a different mechanism. Nevertheless, they have the same risks as all burns, including blistering, sloughing of skin, hair loss
, and permanent damage and scarring. The fact that you have a lot of pain on your scalp is extremely concerning. Usually mild irritation from hair bleach just lasts a few days and may feel like a sunburn. But if you have serious pain, this is the sign of a more serious burn, and this requires immediate evaluation. Failure to undergo proper evaluation and treatment could result in permanent damage to your scalp, loss of hair, infection, and a number of other side effects. As always the diagnosis and the management of your particular concerns will require a physical examination by your personal physician. The symptoms you describe are concerning and should be evaluated urgently by your primary care doctor
or in the emergency room.