I used to worry about this all the time because through out the day I would notice and not remember how I got that bruise. thought it was alters but my treatment providers told me that for some people bruising just happens from something as simple as resting a hand on the lap, or brushing up against something, it can also come from not eating correctly which causes the body to not have the right nutrients to take care of itself like cell regeneration, or strong artery's/vessel walls (bruising is where a vessel or artery wall has been ruptured due to stress, lack of oxygen, anemia, dehydration, high blood pressure, or trauma) even age related problems like menopause can cause sudden and unexpected bruising...short version there are millions upon millions of normal things that can cause a person to bruise easily and unexpectedly. even medications can cause bruising in some people.

then my treatment providers and I worked together on all avenues....with me the problem turned out to be MS (multiple Sclerosis) and medications. once those were in control my unexpected and sudden bruising stopped happening.

Im taking a guess that since the bruise isnt there when you wake up but rather shows up later in the day, that having the nightmares is not connected to it.

my suggestion is keep track of what you were doing just before you noticed the bruise. that will tell you what you are doing that is causing the bruise.

another suggestion is something my treatment providers told me....when you notice the bruise think back to the last half hour to when you felt some sort of physical pain. bruising is like thunder and lightening (first theres the snap of light then there's the thunder) with bruising there is a physical pain then the bruise shows up as the vessel lets out fluid. that will tell you what is causing the bruising to happen.

Another suggestion talk with your treatment providers, they can help you diagnose why you are suddenly bruising easily and unexpectedly.