My 3 Year Old Fell Of The Couch, And Has

My 3 year old fell of the couch, and has a big knot on top of his head. He started crying, and about 3 mins later his nose started bleeding. Not alot, but one nostril was bleeding. He said his head hurt, but calmed down, and fell asleep about an hour later. Should I keep monitoring him, or take him to the ER?