They both mean the same. one is the long version "sort it out" the other is the short version "sort it"
it means to fix, or remedy, put right, correct, solve, overcome etc. for any situation.
the phrase can be used booth positively as encouragement and negatively as a reprimand in anger when someone has done something wrong.
A person scratches your car, you are angry they say they are sorry they will sort it, you say in an angry voice, yes you will sort it..Only British apparently
A person is depressed and worried about something and doesn't know what to do, you say don't worry you will sort it.
The kids have messed up their room , you say clean your room now sort it out.
You drop a box of papers on the floor they have to be put back in order, this is called sorting. [them back into the correct order].