My son, 7, has had a dime-sized deep purple bruise with a pea sized knot on his right cheek with no injury. It showed up about a year ago, took six weeks to fade. The pediatrician wasn't concerned. It returned this past October, and although it has faded, it is still a faint bruise with no knot. We are going on the fourth month this time. Suggestions? He is extremely healthy. 90lbs and 4'5" at age 7