My Three Year Old Son Has Some Sort Of Rash

My three year old son has some sort of rash or bug bites on his legs. Today, both of his feet are bruised, but don't appear to have the bites on them. We took him to urgent care where his foot was x-rayed (at the time we hadn't noticed bruising on the other foot). The doctor didn't seem to care too much about the marks on his legs. Could the bites/rash and bruising be related?