Thanks for writing your query.
The cause of your fall seems to be postural hypotension
, resulting in sudden fall in blood pressure.
You should avoid quick rising from lying down posture and should eat proper diet to prevent hypotension.
The swelling or bump seems to be due to soft tissue injury
Injury of the forehead is commonly associated with black eye and swelling around eyes. Dark discoloration is due to accumulation of blood in the loose tissue of the area around eye.
Headache and swelling will take few days to weeks to heal completely.
Dark discolouration around eyes will take some more time to get resolved completely.
Proper rest will speed up the recovery. You can take anti-inflammatory medicines like Ibuprofen
one tablet twice a day after meals along with an antacid
for relief from pain and swelling.
compress will also be helpful.
If you develop any abnormal symptoms like vomitting, decrease in vision, bleeding from nose or ears, you should immediately seek medical attention.
I hope this is helpful to you.