Can my hair grow back of my hair again after I used warm water on a boil on my head? (photos)

If the infection of scalp caused a damage on hair follicles it mean that you have a cicatricial alopecia and hair will not grow back again .

It really depends on the cause. I’d suggest seeing an expert dermatologist if it doesn’t grow back. He or she will need to rule out a range of conditions including bacterial and fungal infections, carbuncles and even early dissecting cellulitis. Get expert help if things don’t improve. The warm water was unlikely the cause of any significant problems unless you had a burn. 

It may grow back but may not for a couple of months. Best to wait and see at this point. Watch for small fine hairs to appear.