What was the nature of your serious back injury, and what was the treatment you received for it?
Nature of my injury was self harm by scratching my skin until it was bloody.
This covered my whole back btw and looked like scales.
The medication i took was strong antibiotics with some steroids prescribed by my local GP
Seems a bit of an odd sensation perhaps completely unrelated to your injury and healing process. You've stopped the self harm, the scabs have fallen off, right?
A harmless step might be to apply plain skincare lotion to the affected areas after each bath or shower (in case the skin sensation has to do with your skin having become deficient in natural skin oils, the skincare lotion replaces those, especially if done while the skin pores are still open from being exposed to water).
Additional related steps for the same purpose would be: switch from hot water showers & baths, to tepid water; and pat dry do not rub dry when drying off.
Have you found and been using alternative outlets for your nervous tension, or found calming routines to practice?
While my body has completely healed and i no longer self harm i do find that my body scars very easily and heals slowly and very susceptible to infection even when handled in a sterile environment.
Well if you need to live isolated from a non-sterile environment, then regular plain skincare lotion might be slightly risky -- testing its use on a small area at first would be prudent.