Is Small Indentation With Bruise On Head Of An Infant After A Fall A Cause For Concern?

my 7 month old fell off of a lounge chair which is about 1 ft off the ground onto an olympic bench bar weight plate which is about 8 inches....we took him to a doctor who told us not to worry, he did cry and respond normally after words and a visible knot, or swelling came after, it did bruise and now there is a small dent less than an inch and maybe a small line following, when we message or touch it, it does feel lie and indentation and maybe a hill or bump still...? is this some sort of fat or tissue damage or a skull fracture concern