Hi,
Welcome To HCM & Thanks For Asking Your Query Here
if there is no history of trauma and than there are many many reasons of a Sudden unexplained bruising or blood spots under the skin
it may be caused by a medicine, such as aspirin or blood thinners (anticoagulants) ,Infection(sepsis), A bleeding or
clotting disorder, such as
hemophilia, von Willebrand's disease,
thrombocytopenia.
-Other diseases that affect clotting. Examples include:
Chronic inflammatory diseases, such as lupus ,Liver disease, such as
cirrhosis.
however rarely but it can also be caused by Some types of cancer, such as Hodgkin's disease, leukemia, or
multiple myeloma.
so it needs thorough medical check up and investigations to spot a confirm diagnosis
Medical treatment for abnormal bruising or blood spots focuses on preventing or stopping bleeding, changing or adjusting a medicine that may be causing the bruising, or treating the medical problem that is causing the bruising
finally i would strongly suggest you to see Your dr , he may go for all necessary medical investigations to rule out any underlying medical condition
I hope it help
Thanks & Get well Soon