Baby boy has a rash.

My baby has a purple almost bruised like spotted rash allover his right leg that also looks mockly purple at the bottom of his leg. I will pop a picture below we spent a full day in the children’s hospital yesterday and didn’t get discharged until 10:30 last night. Doctors where extremely concerned as the rash does not disappear they took bloods but they where all clear doctors have said my boys rash is very strange he is very well in himself and doesn’t seem unwell they had monitored him all day to see if there was any changes such as his rash spreading or getting worse or him becoming poorly but he was fine and still is now. They

mentioned meningitis and Sepsis but explained that he is too well for it to be anything like that, in the end we got discharged and have been told to keep a close eye on him he’s still fine now but still has the rash. I’m just wondering if any of you mums have seen this sort of rash before or heard of something similar or even been through this I’m so scared that we may have been sent away and they might have missed something which is very rare I know but it does happen and i just can’t help but worry until this rash has gone completely I’m going to be on edge. Pic of rash below