Sounds like the cartilage between the ribs is torn.
Hurts like hell but definitely get it checked out by the doctor.
I know, my son jumped on my chest when he was 3.
Took 3 months to heal.
Thank God he wasn't 4.
C30F Power Up needle
2 turns out
Baffle out, Screens In
It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas