Hello. Welcome to hcm.
As you slipped and feel,you had put lot of pressure on your left foot. So a ligament by name lateral ligament wil be stretched n some time there might be a fracture
. So there wil be swelling also.
I advice you to take a x ray
of foot. If no fracture,then you should apply crepe bandage for 3weeks with pain killers n minimal weight bearing. If fracture is present,POP cast can be put.
All the best