If you replaced counter or other pieces, it may also be off-gassing of those but is most likely the sealant "curing". Yes, in both cases, over exposure is toxic. Ventilate the area until the smell ceases. If it does not, contact your installer and ask about the products used. They may need to come out and redo it with a more Eco friendly product (and YES, those DO exist but are often a bit more expensive). Hope that helps.

Thanks for your input.