Thanks for writing to us.
The best treatment is to remove that flap if it is small and do dressing with 2 % mupirocine cream.
This flap will cause lot of irritation and will also allow bacteria to grow under it. This will further increase the infection.
If the flap is bigger and wound is deep please meet your general practicenor. If it is small remove by yourself. Clean it with betadine
solution and then apply mupirocine cream daily twice for 5 days. You mentioned yellowing that means infection is developing so it will be good to take an antibiotic.
Also please dont cover it with band aid this again increased humidity and infection. Studies have proved that small wounds if treated open by applying anti bacterial cream like mupirocine they heal better.