Do your best to keep soap away from the wound as it can cause irritation.
Tape this dressing on using some Fixomull (Hypoallergenic Adhesive Non-woven dressing tape) and aim to leave it in place for a number of days. These are amazing, they have a gel-like substance impregnated in the dressing that acts like a layer of skin, cooling and protecting the exposed skin below.
If you have a significant rash wound apply a Duoderm ( dressing. Have another look to check for any foreign objects in the wound.
You have exposed multiple nerve ending on the skin to the open air and there are a bunch of pain receptors there!! Once the pain subsides and it will, eventually give the rash area a gentle clean with a soft wash cloth, removing gravel and dirt from the wound.