EEA (fm) immigration status change

[cyrious]

Hello everybody.
I am very confused about something and I hope someone can help me out.
my mom is a eea national working in the uk. i have been given a residence card as eea (fm) some months ago because she is my sponsor, but now I've got my Spanish citizenship through naturalisation of which I had already applied before coming in uk. my question is what should I do now:
1. should i let home office know about it or it does not matter.?
2. can apply for a registration certificate? with the home office knowing that I have a residence card .
thank u...