it seems that you might have warms infestations in your intestinal tract so,while passing stool you may pass warms and it gives itching sensations.Due to nail scratch-marks you may get some infections and small bumps may be formed.
apply some anti-biotic cream or Vaseline on the part.
for itching, you can take tablet cetrizine
go for stool test
for ova and cyst
rule out fungal infection
on the part.
ok and bye.