hello and welcome,
the reccurring purple spot can be recurrent aphthous ulcer minor .it is precipitated commonly in stress
it is also called as aphthous stomatitis
in this case,there is no history of prodromal symptoms.
it can be due to vitamin-b deficiency.
in such cases usually prescribed medicines are-tab.flanzen-10mg,thrice daily for 3 days and tab.wysalone-5mg,thrice daily for 3 days.
hope you get well soon.