belly button maintenance

My baby is 12 days today and yesterday I noticed some dry blood in her belly button (now her umbilical cord fell off at like 4 days old) so I cleaned it with a Q tip and some warm water but a couple hours after that I went to change her diaper and her belly button was filled with blood. Like when you pick a scab. So I decided maybe it was a better idea to let it scan up and heal like that. But now inside her belly button is completely black and scabbed. Should I clean it? Call the pediatrician? Etc. I'm kind of worried but this is my first baby so I'm not so experienced