Literally: full – person – start/injury – injury
Alternately: One’s entire body is covered in wounds. (The specific image is having been cut many times by bladed weapons.) Hurt through and through. By extension, being in a psychic state of pain due to fierce criticism or social attack.
Notes: Some people apparently replace 満身 with homophone 慢心, “conceited pride,” which – although evocative in its own right – is considered an error.