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Generally the symptoms appear within 48 hours to two weeks. However no head injury should be ignored. If you develop nausea, vomiting, excess sleep, severe headache, difficulty in walking and balance, tremors, seizures, vision problems, ringing in ears etc then consult a doctor immediately. These symptoms develop if there is a brain injury or bleed. Otherwise this pressure pain will go in a few days. Take care!
A pedeatrician explained something to me in light of my daughter hitting her head on the ground riding her bike in the yard.
She screamed in fear until the adult in charge found me. She was redfaced when I saw her.
She calmed down when she had me.
The lump on her head was the size of a jumbo egg. Very scary looking.
The doc explained that the scalp is very vascular. It covers the skull, which is an "immovable object". When she hit her head, it caused bleeding under the skalp. (Bruise) Because the blood has nowhere to go, being on top of the immovable skull, it forms what we always called a "goose egg". There can be an impressive bump! with no real damage to the brain. She was fine.
My point is going towards the drinking aspect of your evening. ETOH will numb you so you don't realize you have bumped your head hard enough to bruise it. I have had more than my fair share of ETOH. I was a bartender. I have observed that it seems to thin the blood a bit. So you bleed easier. Or maybe you are more likely to have an elevated blood pressure, doing physical things that you would not ordinarily do (hence the idea of "reduced inhibitions"). Doing things that cause you to bruise your scalp, and wake up with a "goose egg".
Unfortunately you may have to figure out if the headache is from the ETOH, or a brain injury.
With a hangover you may also experience nausea, vomiting, excess sleep, severe h/a, dificulty walking, balance issues, tremors, vision problems, and ringing in the ears. I would not eliminate seizures from the spectrum.
For a hangover, hydration will help the headache, and other manifestations. (ETOH is a diuretic)You would feel much better, in a day or so. The bump is a bruise, and like a bruise it will hurt on the surface.
Head injury symptoms(like the energizer bunny) keep on giving... I had symptoms for two years... A h/a for months.