toddler bumped his head


my 21 month old whacked his forehead off the pavement two weeks ago when he fell. there was a red nark and a lot of crying but he quickly recovered and he has been fine since it happened. I suffer from anxiety and i read an article about head injuries and now im worried it has done some lasting damage to his brain but without me knowing. im so worried and im not sure if i should get him checked even though its been 2 weeks. i feel so bad for not getting him checked out on the day but he seemed compleyely fine and still does. appreciate any advice or similar experiences.