you can let them play together out of the cage under your supervision, but don't let them stay in the cage alone together because the one will want to "groom" the scab.
A hard scab is not always a good sign. Sometimes, it can hide an abscess underneath. Your vet should be able to look at the scab and tell whether or not is is "healthy" tissue or whether it needs to be removed so new tissue can grow.
If it is a small wound, it can heal and fur can grow back in a month or a month and a half. You can post pictures if you want so we can see...