Thank you for your query.
It is very unlikely that the injection site should hurt your daughter 8 months later. You have done the right thing by applying warm compresses. Neosporin
application will not have any effect. I suggest that you consult your doctor who shall examine the lump and guide you accordingly.
In case a needle has broken and left at the injection site it can be confirmed by a x-ray or ultrasound
I hope I have answered your query to your satisfaction.
Wishing your daughter an early recovery.
Rajiv K Khandelwal