Why Is My Toddler Continuously Vomiting After Being Hit On Head?

My 2 yr old son hit his head about 2pm at a trampoline park it s all padded but he hit it pretty hard, since about 4 he s been throwing up non stop almost 3 hours now. In between he keeps going back to sleep then waking up gagging trying to throw up again. Should I take him to er for possible concusion