Yup - needs to go to A&E - compression of the spine can be bloody painful and dangerous. Could be a neck injury - that'll cause bad head pain and I'm sure I don't need to tell you can be very serious. Sorry. Don't be encouraging him to walk till he's checked out.
Hmm - my mother (in her youth) cracked her skull falling hard from a drop on to her bottom! My sister got concussion as a child falling on the ice - also on her bottom first although she also hit her head. The shock and compression transmitted up the spine apparently. So it is better IMHE (nonmedical)to treat such hard falls followed by headache/palor as a head injury. Hope ds is looking and feeling better today.