Son hit his head

My son is 4 months old and I was holding him over my shoulder when he banged his head on my wood headboard. And he’s the one who did the head motion of banging it like when he head butts us so it was a hard hit! He cried of course for like a minute and then I fed him and he seemed fine. There’s no bruise and it’s bed time so he’s sleepy anyway. I know they say vomiting too but he’s a baby and he spits up after he eats anyway so what else do I look out for? He has a drs appt tomorrow for his 4 month checkup and shots, is it okay to wait until then to see a dr?