What Causes Persistent Bleeding Nose In A 4 Year Old?

hi,my child is turning 4..we went to the beach to attend a party,when we return home he s temperature rise and have fever..on monday morning spots started to show,and i learned its measles. I didnt worry that much cause I know he take the MMR vaccine,i did a few research about the virus and it said that it only last for 5 days to one week. He has cough at that moment,good thing i read that its not good to give him cough medicine while on measles (if its true)..what i notice is,his nose bleeds..i check on it and find a wound...so i did not worry much,for two mornings i wake up to see his nose clogged with blood clot,so i just cleaned them knowing their from the wounds. But after the wounds healed,last friday i notice that every time he cries i see blood coming out. And this tuesday morning i saw it after cleaning his nose and his temperamental again,his nose bleeds