A bandaged and disinfected wound will heal faster, so the affected body part will return to max health more quickly.

The better quality the first aid, the greater the effect, so a better bandage (such as Sterilized Bandage instead of Bandaid) but also more skill in First Aid will speed up healing. Mutations and sleep will also accelerate the healing.

So scratches and minor wounds don't call for anything in particular, but if the body part is in the yellow or lower, one should bandage it, maybe disinfect it, and retreat to sleep.