Less severe stomach ulcers do typically heal on their own eventually even without medical treatment.
However if the stomach ulcers are more severe then those severe stomach ulcers may require medical treatment to get rid of the ulcers and heal the ulcers up.
When I had some ulcers before they eventually healed up after a few months without medical treatment.
If the ulcers don't start healing within a few months to 6 months or the ulcers seem to get worse then I would recommend seeing a doctor about the ulcers to get medical treatment to heal up your ulcers.
As long as you have no other complications Peptic Ulcers will usually go away on their own and heal on their own without treatment.
But the ulcers may come back if you have an H. pylori infection that is not successfully treated.