Is Marble Sized Lump With Red Spot On The Head Of An Infant Due To Being Hit Normal?

My daughter is 8 months old and hit her head on the corner of a table and has a marble size lump. She is acting very sleepy, but not seeming to be in any discomfort. Her pupils look normal as well, do I have any need for immediate concern or is it ok to let her sleep. I should also mention at first the bump was rather large where she hit her head, it is now just marble sized bump with a purple/red spot where she hit the corner hard. Thank you for your advice