Can someone talk me (a sufferer of health anxiety) down, I found a bruise on my baby.

Info: my baby is 6 months old and isn’t crawling but rolls around everywhere (but we have carpet)

I was doing his bath time routine tonight and I noticed he had a light bruise on his right leg about 2 inches long and 1 inch maybe wide.

I have NO idea how he got this given that he is not a crawler and a quick google search led me to that it’s extremely rare for a non crawler to get bruises and the options were child abuse and leukemia. Obviously my child is not being abused so all I can thing is he has leukemia.

I have never noticed a bruise on him before and I’m freaking out. Is this a rational fear? Shall I book a doctors appointment?