Friend carried 9 foot inflatable pool float in front of me up stairs. got hit right on top of head from tail end of float. didn't hurt. later developed nausea/headache. was drinking champagne in sun outside w/o much water. chance of concussion?

With this scenario: -being out in the heat, drinking alcohol & lack of other fluids may be the cause of your symptoms. I am assuming that you were bumped with a soft, inflatable device. I would get out of the sun, rest & hydrate with water for the time being.

Concussion: Youmay be suffering from a concussion. See a doctor as soon as possible who can assess for concussion and rule out an intracranial bleed

It can be concussion: It can be concussion or can be other kind of head injury ,I will not wait and try to see a PCP asap

Likely concussion: However recommend assessment as per other answer somewhat urgently to exclude the possibility of other more serious injury. If turns out to be conucussion and ongoing symtpoms then most countries have head injury/concussion services that can assist.

Low: The inflatable pool float could NOT have been so heavy as to cause any visible bleeding, loss of consciousness, or serious injury, could it? I HIGHLY doubt you had a concussion unless you fell down the stairs & injured yourself some other way. More likely, that champagne & heat dehydrated you. Drink plenty of water & fluids, not alcohol. See your doctor nonemergently or use HealthTap Prime. GL.