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If the wound is not infected there is no need to worry about it, but there is definitely a risk for endocarditis
if it gets infected. take the following precautions
get a good antibiotic cream to apply locally over the wound site (like sodium fusidate ointment)
Keep the wound site clean and dry
Let there be a dressing on her ear (pierced site) all time
take good care of wound
Your cardiologist should have given you some prophylactic antibiotic, have a consultation with him (Very important)
If you could not get your cardiologist atleast if possible consult a local pediatric specialist for systemic antibiotic regimen suitable for her.
In case of any suspicion of infection contact a surgeon (ENT surgeon or General surgeon
who can take good care of wound) immediately.