Just trim the stringy thing hanging from abdomen up to scab not the big scab on abdomen. Leave big scab alone let it heal on its own. From looking at pic from days ago cord was dried up then.
It is just like a piece of string hanging from abdomen it is all dried up no blood or nothing going to come from it. You're not cutting large scab from abdomen, just dried up umbilical cord it is done every day to human baby's before it is even dried.
Now that the umbilical cord hanging is dried up you can trim it off, so it doesn't get caught on something or other chicks pecking or pulling and pull-on abdomen. Hoping things go well for you and your chick. GOOD LUCK