Bump on baby’s head?!?

SmA

Does this look bad?!! I’ve never noticed it till now it’s always been a little bumpy but this seems pretty extreme to me??!!! He just learnt to sit and has fallen back into his head a few times over the course of a couple weeks when I’m not fast enough to catch him. But it’s on soft carpet floor and it doesn’t bug him when he does fall back. He’s 6 months almost. Is this concerning!! I’ve just never noticed it maybe??