the pierced part has got infected.
so blood & pus came out.
you should apply & take antibiotic if it is same now.
any infected/injured part heals by fibrous tissue like collagen
these fibres are not like normal tissue.
they are hard & contractile.
so due to healing process a tiny ball is felt.
if it is not blocking the whole then no problem.
but if opposite then consult a dermatologist
for reducing scar formation.