If the leg ulcer is being properly treated and cared for then the leg ulcer should fully heal within 2 to 3 months.
In rare cases some more serious leg ulcers never fully heal or heal at all.
But you need medical treatment to get the leg ulcer to fully heal and prevent infection.
Leg ulcers are treated by a healthcare professional trained in compression therapy and then you have to dress and care for the wound.
If left untreated then the leg ulcer may get worse so you should always see a doctor or go to urgent care to get treatment for the leg ulcer so that it doesn't get further infected.
Leg ulcers can be painful while healing which is normal and the leg ulcer should be healed up within a few months or so but if not then see a doctor about it.